the star formation newsletterthe big diﬃculty are the high shock speeds required to ex-plain...

THE STAR FORMATION NEWSLETTERAn electronic publication dedicated to early stellar/planetary evolution and molecular clouds

No. 274 — 15 October 2015 Editor: Bo Reipurth ([email protected])

The Star Formation Newsletter

Editor: Bo [email protected]

Technical Editor: Eli [email protected]

Technical Assistant: Hsi-Wei [email protected]

Editorial Board

Joao AlvesAlan Boss

Jerome BouvierLee Hartmann

Thomas HenningPaul Ho

Jes JorgensenCharles J. Lada

Thijs KouwenhovenMichael R. MeyerRalph Pudritz

Luis Felipe RodrıguezEwine van Dishoeck

Hans Zinnecker

The Star Formation Newsletter is a vehicle forfast distribution of information of interest for as-tronomers working on star and planet formationand molecular clouds. You can submit materialfor the following sections: Abstracts of recentlyaccepted papers (only for papers sent to refereedjournals), Abstracts of recently accepted major re-views (not standard conference contributions), Dis-sertation Abstracts (presenting abstracts of newPh.D dissertations), Meetings (announcing meet-ings broadly of interest to the star and planet for-mation and early solar system community), NewJobs (advertising jobs specifically aimed towardspersons within the areas of the Newsletter), andShort Announcements (where you can inform or re-quest information from the community). Addition-ally, the Newsletter brings short overview articleson objects of special interest, physical processes ortheoretical results, the early solar system, as wellas occasional interviews.

Newsletter Archivewww.ifa.hawaii.edu/users/reipurth/newsletter.htm

List of Contents

Interview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Perspective . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6

Abstracts of Newly Accepted Papers . . . . . . . . . . 11

Abstracts of Newly Accepted Major Reviews . 47

Dissertation Abstracts . . . . . . . . . . . . . . . . . . . . . . . . 48

New Jobs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Meetings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52

Summary of Upcoming Meetings . . . . . . . . . . . . . 53

Short Announcements . . . . . . . . . . . . . . . . . . . . . . . . 54

Cover Picture

The HH 24 jet complex emanates from a densecloud core in the L1630 cloud in Orion which hosts asmall multiple protostellar system known as SSV63.The nebulous star to the south is the visible T Tauristar SSV59. Color image obtained based on thefollowing filters with composite image color assign-ments in parenthesis: g (blue), r (cyan), I (orange),Hα (red), [S II] (blue). The images were obtainedwith GMOS on Gemini North in 0.5 arcsecond see-ing. The field of view is 4.2x5 arcminutes, and theorientation is north up, east left.

Images by Bo Reipurth and Colin Aspin.Color mosaic by Travis Rector.

Submitting your abstracts

Latex macros for submitting abstractsand dissertation abstracts (by e-mail [email protected]) are appended toeach Call for Abstracts. You can alsosubmit via the Newsletter web inter-face at http://www2.ifa.hawaii.edu/star-formation/index.cfm

Manuel Gudelin conversation with Bo Reipurth

Q:What was your thesis about, and who was your adviser?

A: It all happened somewhat by chance. After my under-graduate studies in theoretical physics at ETH Zurich, Iwas torn between pursuing a PhD in theory (I was muchattracted – and still am! – by fundamental physics likequantum field theory that blossomed at ETH) or rathergetting back to my deep interest since my childhood, name-ly astronomy. Luckily (I would guess) I followed the callingof my heart and decided in favor of astronomy. I was fortu-nate that Arnold Benz offered me a PhD position at ETHto work in plasma astrophysics and on the solar corona.That was the best of all worlds for me – concepts of mag-netic fields in plasmas and radiation propagation pleasedmy theoretical streak. I worked on the interpretation ofthe shortest, millisecond solar radio bursts resulting fromunstable coronal particle distributions. I had enough timeto also spread out into other fields, like the theory of soli-ton propagation in a multi-fluid plasma, numerical parti-cle simulations (with a few thousand particles to follow -a good standard at the time!), and observations with theVLA and other big radio dishes to look for solar analo-gies in the radio emission of low-mass stars. My generousmentor thus paved the way for my future career.

Q: Your observational work started at radio continuumwavelengths, but you soon switched to X-ray studies of stel-lar coronae. What motivated this change?

A: Solar radio astronomy offered, and still offers, excitingresearch and physical insight but it takes place in a rela-tively small and somewhat isolated community. I wantedto apply solar concepts to the bigger world of stars and in-vested my first one-year postdoc grant to give up on solarphysics and move into stellar radio astronomy. I was ob-viously not aware of the risk such a full-blown turnaround

entails for a career in the absence of a long-term fundingperspective, but it somehow worked, and diffusing intoother research areas has become an important constant inmy career ever since – I never regretted it! I joined JeffLinsky’s group at JILA, University of Colorado in Boul-der, an exciting environment to put my plan into action. Iworked on linking coronal particle acceleration (traced byradio emission) with coronal heating (traced by X-rays).Those years, the early-to-mid nineties, were a golden ageof X-ray astronomy with new space observatories launchedalmost every other year (ROSAT, EUVE, ASCA, Bep-poSAX and others). It gave me the opportunity to moveinto X-ray astronomy and stellar coronal research. We dis-covered what I thought was to be expected from solar flarephysics, namely a linear correlation between the radio andX-ray luminosities of active stellar coronae. Arnold Benzand I interpreted this finding quantitatively as evidencefor continuous heating by particle beams accelerated likein solar flares. The correlation was good enough to pre-dict radio fluxes from X-rays from very hot (>10 milliondegrees) coronal plasma. Thus came our first radio dis-coveries of young Suns (first EK Draconis, the star thathas guided my career to the present day), rather preciselyat the predicted flux level. The correlation is by no meansuniversal – it applies only to very hot coronae of activestars (and fails miserably for our Sun!). This point wasunfortunately often ignored and led to some misunder-standings. In any case, we left it there, and if it was ofany interest at all, it was referred to as the ”radio–X-rayluminosity correlation”. About a decade later, the newlydiscovered radio and X-ray emitting brown dwarfs werefound to severely violate our correlation; ironically, thiswas the moment when colleagues started referring to the”Gudel-Benz relation”. Obviously, the interest in differentphysics was awakened.

The rich harvest from the X-ray satellites was also ideal tostudy stellar activity evolution. By sheer luck, I met EdGuinan in a half-empty lecture hall of a solar conferencea seat row in front of me; we were both silently workingon papers about EK Dra - without knowing of each other!A chat in the coffee break started our joint studies of the”Sun in Time”, including X-rays; planetary atmosphericphysicists later used this work to study planet evolution– especially people in Austria where, in a funny turn ofevents one and a half decades later, I found my new home.

Q: Why did you turn your attention to star formation?

I was lucky to obtain a tenure-track position in Switzer-land after my third postdoc year abroad and requestedtenure after another two years. Now I could diffuse eas-ily into new fields with less career risk; I engaged myselfin large space projects for which our institute developedinstrumentation. I became a science Co-I of the XMM-Newton Reflection Grating Spectrometer (RGS) and took

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the position of the Swiss Co-Principal Investigator of MIRIon JWST (which I’m keeping at ETH Zurich in parallelto my new job in Vienna). With Spitzer and Herschel onthe horizon, my fascination for young stars, and the manynew X-ray findings in star formation, I got interested instudying the influence of high-energy, ionizing radiationon stellar environments, specifically protoplanetary disks,which led to fruitful new projects and collaborations. I amconfident that JWST will push this field much further.

Q: T Tauri stars (TTS) are often X-ray emitters. Whatis the basic mechanism?

A: TTS X-rays were discovered in the early days of X-rayastronomy. They are akin to X-rays from other young,active stars and so are thought to be coronal. Strongmagnetic fields abound on T Tauri stars, after all. Thereare some interesting, distinctive properties of classical TTauris (CTTS), however. For the same bolometric lu-minosity, they are statistically about half as X-ray lu-minous as weak-lined T Tauris (WTTS). Perhaps accre-tion streams completely absorb some X-rays. Also, CTTScoronae are systematically hotter than WTTS coronae, aresult obtained by one of my graduate students, Alessan-dra Telleschi. We don’t understand this feature yet.

An interesting turn came when Joel Kastner et al. sug-gested that the unusually soft X-rays from TW Hya areproduced in accretion shocks. The model is not easy toprove and faces some problems with photoelectric absorp-tion but it was an important step. When we looked athigh-resolution CTTS X-ray spectra, we discovered sys-tematic excess emission in the Ovii lines compared toWTTS, a feature we dubbed the ”X-ray soft excess”. Clear-ly, accretion adds a lot of moderately hot (∼ 1 MK) plasmato the otherwise much hotter coronal plasma. Nancy Brick-house et al. subsequently proposed that accretion drivesmaterial flow from the accretion hot spot into coronalloops from where X-rays can easily be observed.

Q: You have studied X-rays from Herbig-Haro jets, anddiscovered X-ray emission from the DG Tau jet. Variousmodels exist to explain the data, what is your view?

A: We know two types of sources, those at the workingsurfaces of HH objects far away from the star, and thosein the jets very close to the central engine. Shocks are usu-ally held responsible for the X-rays, either forming againstthe interstellar medium or between plasma blobs in the jet.The big difficulty are the high shock speeds required to ex-plain plasma temperatures of 4-6 MK. In a collaborationled by Stephen Skinner, we suggested that high-speed plas-moids ejected by the star or the star-disk magnetic fields(like coronal mass ejections) are guided along the jet toeventually collide further out and produce the X-rays. Aninteresting possibility is local heating by magnetic recon-nection. We need a better insight into jet magnetic fields!

In my own Chandra campaign on protostellar X-ray jets,among them DG Tau B, we found strongly absorbed stellarX-rays but no jets. I was vaguely aware of the CTTS DGTau nearly an arcminute north of DG Tau B but initiallydidn’t pay attention. But there was this fuzzy cloud of afew excess X-ray counts around it. It turned out to be thetrace of a luminous X-ray jet. The most fascinating featurewas DG Tau’s X-ray spectrum – composed of two entirelyindependent components which we now know to be a softcomponent from the jet very close to the star (20-30 AUand closer) and a highly absorbed component from a veryhot, flaring corona. The absorption lacks the expected,accompanying dust extinction; our model for these ”TwoAbsorber X-ray” (TAX) sources posits that absorption isdue to dust-depleted gas streams close to the star, mostlikely the accretion streams but maybe also disk winds.

Q: You led the major “XMM-Newton extended survey ofthe Taurus molecular cloud” (XEST). What were the mainresults?

A: XEST was a real adventure. In early 2003 I calledThierry Montmerle to check his opinion about my some-what eccentric idea to map 5 square degrees of Tauruswith XMM-Newton. He bursted out, ”are you crazy??But then this is interesting!” And off we went. With ateam of about two dozen, XEST was set up to surveya nearby, low-mass star-forming region devoid of mas-sive stars; it complements the Chandra Orion UltradeepProject (COUP) led by Eric Feigelson in many ways. Wedid not have the luxury of integrating over nearly twoweeks but with fluxes on average about ten times higherand a larger collecting area, XEST got excellent spec-troscopy of many targets and collected the largest high-resolution spectroscopy sample of CTTS plus Herbigs atthe time. The major strength of XEST was therefore inthe physical characterization of the X-ray sources ratherthan in the time domain but we did some flare studiesas well. We could confirm important trends (correlationsbetween X-rays and bolometric luminosity and betweenX-rays and stellar mass, etc) but significantly less com-promised by scatter and error bars. XEST showed thatthe two relations just mentioned are not independent. Wealso found some weak negative correlation with the accre-tion rate and a slight decline of X-rays with age.

A big boost came from XMM-Newton’s RGS that led toour discovery of the CTTS ”X-ray soft excess”, and also tothe first detailed spectral X-ray characterization of a Her-big star. AB Aur showed both an anomalously soft spec-trum and a periodicity known from optical observationsof the Herbig star so that ambiguities related to possiblelate-type companions were removed for the first time inX-rays. XEST also provided a large sample of ultravioletflux measurements and flare observations. Other findingsrelated to jets, CTTS rotation, and coronal composition.

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Q: Most recently, you and colleagues have studied the ef-fects of X-ray and UV radiation on the habitability of exo-planets and have summarized your ideas in a major reviewin Protostars and Planets VI. What are the key points?

A: Our habitability project has its own funny history.Around the time (2009) when I accepted a chair at theUniversity of Vienna, I attended a small science meetingin Graz where a group of scientists around Helmut Lam-mer studied planetary atmospheric loss driven by stellaractivity. They in fact used results from my X-ray studiesof the Sun in Time in the nineties. As my move to Vi-enna was imminent, we seized the opportunity and kickedoff discussions toward a large, national program on hab-itability. The two-year-long painstaking preparation andevaluation of this major project succeeded beyond any ex-pectations and against all odds, and I am deeply hon-ored to now lead a team of over forty junior and seniorscientists in Austria, involving many international collab-orations. The key objectives start with star formationand protoplanetary disks as the latter are the factories ofimportant molecules, but also regulate protoatmosphericaccretion onto growing planets. This also gives me therewarding opportunity to add new research perspectivesto my interest in star formation. Our team further ad-dresses the high-energy evolution of the host star startingat the time of planet formation. In what returned myattention to my early postdoctoral studies of the Sun inTime – and rewards my decision to jump between var-ious research fields in my career –, we just published aself-consistent activity evolution model for low-mass starsincluding rotation, spin-down, wind mass loss, magneticactivity and high-energy emission. In these models, hab-itability evolution strongly depends on initial conditionsat the T Tauri stage. Other teams within the projectdeal with small-body collisions to study water transport toplanets in the habitable zone; such calculations require hy-drodynamic simulations including solid-state features suchas crack formation and stress. Another important area isdynamics in multi-planet systems, planetesimal disks, andbinary stellar systems. We are presently going through theevaluation of the continuation proposal phase (formulatedin a 493-page document) to obtain support until 2020.

Q: You are head of the Star and Planet Formation Groupat the University of Vienna. What other topics are youand your group working on?

A: I am proudly leading a terrific 400% group: 50% exo-planets–50% star formation; 50% postdocs–50% grad stu-dents; 50% theoreticians–50% observers; and 50% female–50% male. Jets and protoplanetary disks are one of thekey topics. We are partners in a European project on diskmodeling using archival samples. Our goal is to interpretmulti-wavelength disk data including stellar irradiationto self-consistently model the thermo-chemical structure

of disks. We would like to better understand how disksevolve in time, and are also performing advanced hydrosimulations. We have secured and interpreted the first X-ray observations of a bona-fide FUor in its early outburstphase. We discovered large columns of dust-depleted gas,probably related to accretion streams or disk winds.

Q: Astronomy in Austria has seen a major rejuvenationand expansion in recent years, and star and planet forma-tion has been strengthened. What has driven this welcomedevelopment, and what are prospects for the coming yearsfor Austrian astronomy?

A: As a recent (2010) immigrant from Switzerland, I’mstill trying to understand the complexities of Austrian as-tronomy during the past decades. It is a ground truth thatAustria became a member of ESO only in 2008, despite en-ergetic efforts undertaken by a number of forward-lookingastronomers back to the seventies. In a small country likeAustria, the way forward is to unite and speak with onevoice. I think this didn’t happen for too long; groupsworked in relative isolation and were supporting small,local telescopes. Only in 2002, the Austrian Society forAstronomy and Astrophysics was founded; one of its ma-jor goals was to establish Austrian membership in ESO.Negotiations with the ministry were far from easy but fi-nally succeeded. Then, the institutes used the fresh mo-mentum to negotiate new astronomy university chairs toeffectively strengthen the science return from ESO. Whenthe University of Vienna doubled from two to four as-trophysics chairs and a previous one got vacant, we werethree new professors moving in at the same time (apartfrom myself Joao Alves and Bodo Ziegler); all of us areinterested in galactic or extragalactic star formation andhave proactively argued, each one separately in his appli-cation and negotiations, in favor of modern research usingESO and ESA facilities. Capitalizing on this unlikely suc-cess, each of us engaged into becoming a co-investigatorof one of the planned E-ELT instruments (now METIS,MICADO, and MOSAIC); we then united all astronomyuniversity institutes in Austria once again, also includ-ing mathematicians, to formulate a special request to theministry for a national E-ELT instrumentation program.And once more we succeeded and are on track. The sameis happening with ESA projects where I am enjoying ex-tremely rewarding national collaboration in projects suchas CHEOPS, PLATO, or Athena+. Similar things to sayabout our national organizing committee for the IAU Gen-eral Assembly 2018 in Vienna. Our key program on hab-itability has set up a national collaboration on the scienceside, now actually co-operating with the CHEOPS andPLATO projects. In my view, we are extremely well setup for the next decade and even beyond. But the messageis clear: In a country where every astronomer personallyknows every other, the way to success is to stand together.

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Perspective

Density structure of molecularclouds and star formation

Jouni Kainulainen

1 Introduction

How exactly different physical processes give rise to thestar formation rates of molecular clouds is a decades oldopen question. Most of all, we do not understand howthe different processes mould the structure and dynam-ics of the clouds, eventually causing a (small!) fraction oftheir gas to have conditions favourable for gravitationalcollapse and star formation. Observationally, we knowvery well that the star formation rates and efficiencies ofmolecular clouds depend strongly on the internal struc-ture of the clouds (e.g., Kainulainen et al. 2009, 2014;Lada et al. 2012; Evans et al. 2014). Therefore, the firststep in understanding the regulation of star formation isunderstanding the regulation of this internal cloud struc-ture. This, in turn, calls for a comprehensive, systematiccharacterisation of the molecular cloud structure.

Unfortunately, describing the observed structure of molec-ular clouds is nothing if not confusing. Terms such ascloud, clump, core, and filament are in a daily use in thefield, and an easy way to start an endless debate is toask what these words actually mean. Observations haveestablished that the structure of molecular clouds is frac-tal and hierarchical (reviewed in, e.g., Elmegreen & Scalo2004); characterising such structure by discretising it un-avoidably delivers a very biased and/or reduced picture.

However, right now is the Golden Age of the cloud struc-ture studies. The new observational techniques and fa-cilities are just about to enable us to build a new view ofmolecular clouds based on the statistics of their structuralcharacteristics. In this article, I discuss some recent ad-

vances, and outstanding open questions, in studying onekey statistic of molecular clouds: the probability distribu-tion of their column densities.

2 The missing ingredient

The major analytic theories that have emerged to predictstar formation rates all share a common, quite intuitivegeneral framework: star formation rates are essentially es-timated from the mass of gravitationally unstable gas thatcollapses to form stars in its own free-fall time-scale (re-viewed in Padoan et al. 2014; Federrath & Klessen 2012).Calculation of the unstable gas mass requires knowledge ofthe density distribution of the interstellar medium (ISM).This information is encapsulated in the probability den-sity function of gas densities (ρ-PDF, for short), whichdescribes the probability of a unit volume to have a cer-tain density. While the details of different theories maygreatly differ, most of them employ the ρ-PDF functionas a basic ingredient.

The fundamental missing piece in this approach is thatthe ρ-PDF function has not been observationally well con-strained. Two problems contribute to this. First, the den-sity structure of molecular clouds is not directly accessiblewith observations. Instead, observations can only measurecolumn densities. However today, this problem is allevi-ated by studies that have established transformations be-tween the column density PDFs (N -PDF, for short) andthe ρ-PDFs. These studies have also shown that N -PDFscan carry the same information as the ρ-PDFs (e.g., Bruntet al. 2010; Federrath & Klessen 2013; Kainulainen et al.2014). Second, also mapping column densities is difficult;mapping entire molecular clouds with high sensitivity, andsimultaneously with high spatial resolution, is an obser-vational challenge. Data allowing this have only becomeavailable during the past decade or so.

In lack of observational constraints, the star formation the-ories have turned to numerical simulations for informa-tion about the ρ-PDF function. These simulations haveheavily concentrated in modelling supersonic turbulence,including also other physics (self-gravity, magnetic fields,chemistry) as computational capabilities have begun to al-low it. The fundamental result of the simulations is thatisothermal, supersonic, driven turbulence develops a log-normal ρ-PDF. The important parameter of this functionis its width that is directly coupled with gas physics: itdepends on the turbulent energy of the media, the rela-tive amount of compressive energy, and the magnetic fieldstrength (e.g., Vazquez-Semadeni 1994; Federrath et al.2010; Molina et al. 2012). Consequently, the ρ-PDF is notonly a crucial input for star formation models, but also afundamental prediction of the entire turbulence-regulated

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Figure 1: Left: Column density map of the Ophiuchus molecular cloud, derived using near-infrared dust extinctionmapping (Kainulainen et al. 2009). Right: N -PDFs of a non-star-forming cloud (Lupus V) and a star-forming cloud(Taurus). AV, the dust extinction, is used as the tracer of column density. The red curve is a fit of a log-normalfunction to the peak of the distribution. The N -PDFs of most clouds, i.e., clouds that are forming stars, are poorlyfit with single log-normal functions (Kainulainen et al. 2009. The figures have been prepared with the help of MPIAGraphics Department.).

ISM framework.

In lack of observational constraints, the star formationrate theories commonly adopt this framework and withit the lognormal ρ-PDF. This means that the key ingre-dient of the models, and also the fundamental predictionof the turbulence-regulated ISM framework, remains notconfronted by systematic observations.

3 Universal link between the PDFs

and star formation?

Observational works are now in progress to change thispicture; they are beginning to provide systematic con-straints for the column density statistics of molecular clouds.This progress has been made possible by the novel dust ex-tinction mapping techniques in near-infrared and Herscheldust emission measurements in far-infrared and sub-mm(e.g., Lombardi 2009; Andre et al. 2010). These tech-niques use dust to trace the column density distributionsof the clouds and can provide high-sensitivity maps withresolution that reaches some 0.05 pc in the Solar neigh-bourhood clouds. Such resolution means that the resultingmaps contain hundreds of thousands of independent res-olution elements, enabling studies of the column densitystatistics.

The above techniques have already given us a basic pic-ture of what the column density distributions, N -PDFs,of molecular clouds are like. Now more than six years ago,we performed the first systematic survey of the N -PDFs inthe Solar neighbourhood clouds (Kainulainen et al. 2009).In this work, we analysed dust extinction-derived columndensity maps of practically all clouds closer than 260 pcto the Sun. This work gave rise to two important re-sults. First, we showed that the N -PDFs of most cloudsare poorly fitted with log-normal functions when consider-ing their entire column density range (see Fig. 1). Rather,they showed a possibly log-normal shape only at low-columndensities (N(H) < 4 − 6 × 1021 cm−2), while higher col-umn densities showed a significant, power-law like excessto that shape. This was an important result, as it seemedto at least partially contradict the prediction adopted fromthe turbulence-regulated ISM framework that molecularclouds might carry log-normal ρ-PDF (and N -PDF, e.g.,Federrath & Klessen 2013).

The second important result from Kainulainen et al. (2009)was that the N -PDFs showed a variety of shapes thatcorrelated with the number of young stars in the clouds.Specifically, clouds with more young stellar objects (YSOs)showedmore top-heavyN -PDFs than those with less YSOs.In the extreme of this relation, the couple of clouds in thesample that had no young stars within had very bottom-heavy, close-to log-normalN -PDFs (see Fig. 1). We quan-

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tified this trend better later by showing that the mean starformation rate per unit area in entire molecular cloudscorrelates with the top-heaviness of their ρ-PDFs (Kainu-lainen et al. 2014).

Herschel can map column densities in molecular cloudsbased on dust emission measurements in 18′′ resolution,which is a factor of about four finer than can be achievedwith near-infrared extinction mapping in the Solar neigh-borhood (Fig. 2). Studies employing Herschel data havefound the same trend between the star formation activ-ity and the shape of the N -PDFs (e.g., Schneider et al.2013; Alves de Oliveira et al. 2014). They have alsoraised a question whether the N -PDFs of any clouds arelog-normal, or are all N -PDFs better described by power-laws (Lombardi et al. 2015). The first Herschel studieshave also reached outside the Solar neighbourhood, to-wards more massive molecular clouds in the Galaxy (e.g.,Schneider et al. 2015). However so far, Herschel datahave been clearly underexploited; this is surely expectedto change in the near future.

One great advantage of the resolution provided by the Her-schel data is that it allows us to zoom in and study the N -PDFs within molecular clouds in the Solar neighbourhood(e.g., Stutz & Kainulainen 2015; see Fig. 2). This allowslinking the N -PDFs not only to the mean star formationactivity of the clouds, but also to their local star formationrate and efficiency. In practice, this is possible becausethe protostars are identifiable in the Solar neighbourhoodclouds, e.g., using Herschel data and/or near- and mid-infrared colour selections. The first works taking advan-tage of this have found that also within clouds the numberof Class 0 protostars per unit area correlates with the top-heaviness of the N -PDFs (Sadavoy et al. 2014; Stutz &Kainulainen 2015). This means that within clouds, at thescales of about a parsec, the on-going star formation rateactivity is linked to the local gas mass distribution.

Intriguingly, the first small-scale studies have very recentlyfound that the evolutionary time-scale of parsec-scale re-gions inferred from Class 0 and 1 protostars anti-correlateswith the top-heaviness of the N -PDFs (Stutz & Kainu-lainen 2015, Fig. 2). In other words, regions with moretop-heavyN -PDFs seem to have shorter protostellar time-scales. This is curious, as it suggests that regions withflatter N -PDFs may be younger. Such a result is not triv-ial to interpret in the light of current theoretical modelsfor N -PDF evolution (elaborated in Section 4).

Is the strong relationship between star formation and den-sity distributions also prevalent at Galactic scales? Theanswer seems to be yes. Abreu Vicente et al. (2015) per-formed the first systematic Galactic scale study of the N -PDFs, analysing 330 molecular clouds in the first Galacticquadrant (see Fig. 3). This work used the Galactic planedust emission survey ATLASGAL (Schuller et al. 2009)

Figure 2: Top: Column density map of Orion A derivedusing Herschel dust emission observations (Stutz & Kain-ulainen 2015). The white crosses show the protostars inthe cloud. The boxes show the eight regions in whichthe relation between protostars and N -PDFs was studied.Bottom: Class 0 protostar fraction as a function of the N -PDF power-law slope in the eight regions within Orion A(see the top panel). The y-axis on the right gives the evo-lutionary time-scale assuming a constant star formationrate. Under that assumption, high Class 0 fractions cor-respond to short evolutionary time-scales (Stutz & Kain-ulainen 2015). The grey data points are for the Perseuscloud (Sadavoy 2013, Sadavoy et al. 2014).

to trace the column density distributions. The main re-sult of this work was that indeed, objects that showedno signs of on-going star formation had the most bottom-

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−3 −2 −1 0 1 2 3 4 5

s = ln(AV/AV)

−5

−4

−3

−2

−1

0

log

10 (p[s])

Figure 3: Top: The first Galactic-scale study of the molec-ular cloud N -PDFs, performed using ATLASGAL 870 µmdust emission data (Abreu Vicente et al. 2015; Partial fig-ure credit: NASA/JPL-Caltech/R. Hurt (SSC-Caltech)).The red, blue, and green symbols show the HII regions,star-forming clouds, and starless clumps. Bottom: Thetotal N -PDFs of each object class. The colours are as inthe top panel. The starless clumps (green) have the mostbottom-heavy N -PDFs and the clouds containing HII re-gions (red) the most top-heavy N -PDFs.

heavy N -PDFs. Star-forming clouds that harbour proto-stars had more top-heavy N -PDFs, and finally, the mostactive clouds that contained HII regions had the most top-heavy N -PDFs (Fig. 3). This finding showed that thecorrelation between the N -PDFs and star formation ex-ists also at Galactic scales; therefore, it must represent afundamentally important relation describing star forma-tion in the ISM.

Finally, indications of a similar trend have also been de-tected in external galaxies. Using interferometic observa-tions of CO emission from the entire M51 galaxy, Hugheset al. (2013) showed that regions that had higher sur-face density of star clusters also showed more top-heavyN -PDFs. The resolution of their data was about 40 pc,

roughly corresponding to a size of a giant molecular cloud.These observations again suggest a fundamental correla-tion between the column density structure and star for-mation activity, especially showing its prevalence at thescales of entire galaxies.

4 The outstanding open question:how do N-PDFs evolve?

How can the observed, quite possibly universal trend be-tween the column density distributions and star formationactivity be understood? During the past few years, the ob-servational findings have triggered a wealth of theoreticalworks examining the ρ-PDFs (and usually also N -PDFs).These works have heavily concentrated on analysing the ρ-PDFs in magneto-hydrodynamic simulations of self-gravi-tating, driven turbulence (e.g., Kritsuk et al. 2010; Fed-errath & Klessen 2012, 2013; Ward et al. 2014). Ana-lytic theories have also been constructed (e.g., Girichidiset al. 2014). These works commonly share a framework inwhich an initially turbulence-generated density field in acomputational domain with periodic boundary conditionsis let to evolve under self-gravity (and possibly continu-ing energy injection at large scales). In these simulations,the ρ-PDFs evolve from the initial, turbulence-dominatedstage to a gravity-dominated stage. The shape of the ini-tial ρ-PDF is determined by the properties of turbulence(cf., Section 2), and it is typically narrow, i.e., bottom-heavy, compared to later stages. After a time that roughlycorresponds to the free-fall time at the mean density ofthe model, the ρ-PDFs reach a gravity-dominated stage.At this stage, the ρ-PDFs have developed a power-law-like slope at the high-density side that is approximately inagreement with the flattest observed slopes.

At least qualitatively, the above framework reproduces theobserved variety of N -PDFs. It also provides a possibleexplanation for why non-star-forming clouds have narrowN -PDFs in comparison to star-forming clouds: (at leastmost of) the clouds with narrow N -PDFs are young andhave not yet started to form stars. In the future, theymay evolve by gathering more material to high-columndensities, leading to a more top-heavy N -PDF and activestar formation.

However successful the above framework may at first seem,the evolutionary picture it suggests should be taken withsome caution. Consider this: in this framework, we havea turbulence-generated initial density field; then the self-gravity is (literally) switched on and the model evolvesunder it (possibly without further driving of turbulence).Given this setup, it does not seem a very surprising re-sult to find evolution from a turbulence-dominated to agravity-dominated state. Rather, it seems a quite natu-

9

ral consequence of the initial conditions of the framework,questioning the evolutionary picture predicted by it.

The way forward is to break away from the idealised setupin which the turbulence-dominated and gravity-dominatedphases are separated by construction. Instead, we need tolook into large-scale simulations in which molecular cloudformation, and subsequent evolution, takes place in situ,as a result of large-scale processes. One setup for this is aframework in which two warm gas flows collide, resultingin formation of a colder gas phase and dense gas resem-bling molecular clouds. In this framework, the N -PDFsderived for the entire computational domain evolve from abottom-heavy, log-normal-like shape to a top-heavy, power-law-like shape (e.g., Ballesteros-Paredes et al. 2011). Thissuggests that it may be able to reproduce the observed va-riety of N -PDFs, and that evolution of N -PDFs may bethe ultimate reason causing the variety. However, it is un-clear how the N -PDFs of individual molecular clouds inthese simulations behave, and especially, to what degreethe N -PDFs of individual clouds show evolution. This re-mains an open question that is likely to be answered inthe immediate future. All in all, studying the evolutionof PDFs in global-scale numerical simulations is a topicactively worked on in the field at this very moment.

5 The next five years

The near future of cloud structure/star formation studieswill witness a fundamental advance. This advance resultsfrom the ability to (finally!) link together the processestaking place at the scale of galaxies and those acting withinindividual molecular clouds. On the one hand, the com-putational capabilities are right now starting to allow sim-ulations of entire galaxies in high-enough resolution thatthe internal structure of molecular clouds is well resolved(e.g., Smith et al. 2014). This means that it will be pos-sible to give predictions for the internal cloud structurestatistics as a function of the galaxy-scale environment.

On the other hand, the observations will establish a sys-tematic, Galactic-scale view of the internal cloud struc-ture that can be used to confront those predictions. Thisview will be partly built by full exploitation of the Her-schel data in the Solar neighbourhood. However, reach-ing equally high spatial resolution farther away in theGalaxy requires other techniques. In principle, ALMAcan map molecular clouds at arcsecond-scale resolutionin high-enough sensitivity, but such observing programswill time-wise be expensive, only allowing studies of smallcloud samples. A highly complementary alternative is anovel dust extinction mapping technique that combinesnear- and mid-infrared observations (Kainulainen & Tan2013, Kainulainen et al. 2013). This technique can reach

arcsecond-scale resolution in mapping young infrared darkclouds and their surroundings, making it possible to mapthousands of clouds in the Galactic plane. All together,the above observational approaches will soon create a tenth-of-a-parsec resolution observational picture of the molecu-lar cloud structure in a volume that is relevant for Galactic-scale star formation.

While the previous half a decade saw the coming of sys-tematic constraints for the (column) density distributionsof molecular clouds, the next half a decade will see thegrowth of that picture into the Galactic context. Mostimportantly, this enables us to bridge together the starformation relations observed at the scales of entire galax-ies and the physical processes that regulate star formationwithin individual molecular clouds.

References:

Abreu Vicente et al. 2015, A&A, in press, arXiv:1507.00538

Alves de Oliveira et al. 2014, A&A, 568, A98

Andre et al. 2010, A&A, 518, L102

Ballesteros-Paredes et al. 2011, MNRAS, 416, 1436

Brunt et al. 2010, MNRAS, 405, L56

Evans et al. 2014, ApJ, 782, 114

Federrath & Klessen 2012, 761, 156

Federrath & Klessen 2013, 763, 51

Federrath et al. 2010, A&A, 512, A81

Girichidis et al. 2014, ApJ, 781, 91

Hughes et al. 2013, ApJ, 779, 44

Kainulainen et al. 2009, A&A, 508, L35

Kainulainen et al. 2011a, A&A, 530, A64

Kainulainen et al. 2011b, A&A, 536, A48

Kainulainen et al. 2013, A&A, 557, 120

Kainulainen et al. 2014, Science, 344, 183

Kainulainen & Tan 2013, A&A, 549, A53

Kritsuk et al. 2010, ApJL, 727, L20

Lombardi et al. 2009, A&A, 493, 735

Lombardi et al. 2015, A&A, 576, L1

Molina et al. 2012, MNRAS, 423, 2680

Padoan et al. 2014, in Protostars and Planets VI, 77

Sadavoy 2013, PhD Thesis, University of Victoria

Sadavoy et al. 2014, ApJL, 787, L18

Schneider et al. 2013, ApJL, 766, L17

Schneider et al. 2015, A&A, 575, A79

Schuller et al. 2009, A&A, 504, 415

Smith et al. 2014, MNRAS, 441, 1628

Stutz & Kainulainen 2015, A&A, 557L, 6

Vazquez-Semadeni 1994, ApJ, 423, 681

Ward et al. 2014, MNRAS, 445, 1575

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Abstracts of recently accepted papers

First X-ray detection of the young variable V1180 Cas

S. Antoniucci1, A. A. Nucita2,3, T. Giannini1, D. Lorenzetti1, B. Stelzer4, D. Gerardi2, S. Delle Rose2,A. Di Paola1, M. Giordano2,3, L. Manni2,3 and F. Strafella2

1 INAF-Osservatorio Astronomico di Roma, Via Frascati 33, I-00078, Monte Porzio Catone, Italy2 Department of Mathematics and Physics E. De Giorgi, University of Salento, Via per Arnesano, CP 193, I-73100,Lecce, Italy3 INFN, Sez. di Lecce, via per Arnesano, CP 193, I-73100, Lecce, Italy4 INAF-Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134, Palermo, Italy

E-mail contact: simone.antoniucci at oa-roma.inaf.it

V1180 Cas is a young variable that has shown strong photometric fluctuations (∆I ∼ 6 mag) in the recent past,which have been attributed to events of enhanced accretion. The source has entered a new high-brightness state inSeptember 2013, which we have previously analysed through optical and near-infrared spectroscopy.To investigate the current active phase of V1180 Cas, we performed observations with the Chandra satellite aimedat studying the X-ray emission from the object and its connection to accretion episodes. Chandra observations wereperformed in early August 2014. Complementary JHK photometry and J-band spectroscopy were taken at ourCampo Imperatore facility to relate the X-ray and near-infrared emission from the target.We observe a peak of X-ray emission at the nominal position of V1180 Cas and estimate that the confidence level ofthe detection is about 3σ. The observed signal corresponds to an X-ray luminosity LX(0.5-7 kev) in the range 0.8÷2.2×1030 erg s−1. Based on the relatively short duration of the dim states in the light curve and on stellar luminosityconsiderations, we explored the possibility that the brightness minima of V1180 Cas are driven by extinction variations.From the analysis of the spectral energy distribution of the high state we infer a stellar luminosity of 0.8-0.9 L⊙ andfind that the derived LX is comparable to the average X-ray luminosity values observed in T Tauri objects. Moreover,the X-ray luminosity appears to be lower than the X-ray emission levels around 5×1030÷ 1× 1031 erg s−1 detected atoutbursts in similar low-mass objects.Our analysis suggests that at least part of the photometric fluctuations of V1180 Cas might be extinction effects ratherthan the result of accretion excess emission. However, because the source displays spectral features indicative of activeaccretion, we speculate that its photometric variations might be the result of a combination of accretion-induced andextinction-driven effects, as suggested for other young variables, such as V1184 Tau and V2492 Cyg.

Accepted by A&A

http://arxiv.org/pdf/1509.07730

Star formation triggered by cloud-cloud collisions

S. K. Balfour1, A. P. Whitworth1, D. A. Hubber2,3 and S. E. Jaffa1

1 School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, Wales, UK2 University Observatory Munich, Ludwig-Maximilians-University Munich, Scheinerstr.1, 81679 Munich, Germany3 Excellence Cluster Universe, Boltzmannstr. 2, 85748 Garching, Germany

E-mail contact: scott.balfour at astro.cf.ac.uk

We present the results of SPH simulations in which two clouds, each having mass M0=500M

⊙and radius R

0=2pc,

collide head-on at relative velocities of ∆v0= 2.4, 2.8, 3.2, 3.6 and 4.0 kms−1. There is a clear trend with increasing

∆v0. At low ∆v

0, star formation starts later, and the shock-compressed layer breaks up into an array of predominantly

radial filaments; stars condense out of these filaments and fall, together with residual gas, towards the centre of thelayer, to form a single large-N cluster, which then evolves by competitive accretion, producing one or two very massiveprotostars and a diaspora of ejected (mainly low-mass) protostars; the pattern of filaments is reminiscent of the hub and

11


spokes systems identified recently by observers. At high ∆v0, star formation occurs sooner and the shock-compressed

layer breaks up into a network of filaments; the pattern of filaments here is more like a spider’s web, with severalsmall-N clusters forming independently of one another, in cores at the intersections of filaments, and since each coreonly spawns a small number of protostars, there are fewer ejections of protostars. As the relative velocity is increased,the mean protostellar mass increases, but the maximum protostellar mass and the width of the mass function bothdecrease. We use a Minimal Spanning Tree to analyse the spatial distributions of protostars formed at different relativevelocities.

Accepted by MNRAS


Sh2-138: Physical environment around a small cluster of massive stars

T. Baug1, D.K. Ojha1, L.K. Dewangan2, J.P. Ninan1, B.C. Bhatt3, S.K. Ghosh1,4 and K.K. Mallick1

1 Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai 400005, India2 Instituto Nacional de Astrofısica, Optica y Electronica, Luis Enrique Erro # 1, Tonantzintla, Puebla, Mexico C.P.72840, Mexico3 Indian Institute of Astrophysics, Koramangala, Bangalore 560 034, India4 National Centre for Radio Astrophysics, Tata Institute of Fundamental Research, Pune 411 007, India

E-mail contact: tapas.baug at tifr.res.in

We present a multi-wavelength study of the Sh2-138, a Galactic compact H ii region. The data comprise of optical andnear-infrared (NIR) photometric and spectroscopic observations from the 2-m Himalayan Chandra Telescope, radioobservations from the Giant Metrewave Radio Telescope (GMRT), and archival data covering radio through NIRwavelengths. A total of 10 Class I and 54 Class II young stellar objects (YSOs) are identified in a 4′.6×4′.6 area ofthe Sh2-138 region. Five compact ionized clumps, with four lacking of any optical or NIR counterparts, are identifiedusing the 1280 MHz radio map, and correspond to sources with spectral type earlier than B0.5. Free-free emissionspectral energy distribution fitting of the central compact H ii region yields an electron density of ∼2250±400 cm−3.With the aid of a wide range of spectra, from 0.5–15 µm, the central brightest source - previously hypothesised to bethe main ionizing source - is characterized as a Herbig Be type star. At large scale (15′×15′), the Herschel images(70–500 µm) and the nearest neighbour analysis of YSOs suggest the formation of an isolated cluster at the junctionof filaments. Furthermore, using a greybody fit to the dust spectrum, the cluster is found to be associated with thehighest column density (∼3×1022 cm−2) and high temperature (∼35 K) regime, as well as with the radio continuumemission. The mass of the central clump seen in the column density map is estimated to be ∼3770 M⊙.

Accepted by MNRAS

http://xxx.lanl.gov/pdf/1509.08716.pdf

Accretion disks in luminous young stellar objects

M.T. Beltran1,2, and W.J. de Wit3

1 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy2 Senior Scientific Visitor at ESO Chile3 European Southern Observatory, Alonso de Cordova 3107, Vitacura, Casilla 19001, Santiago de Chile, Chile

E-mail contact: mbeltran at arcetri.astro.it

An observational review is provided of the properties of accretion disks around young stars. It concerns the primordialdisks of intermediate- and high-mass young stellar objects in embedded and optically revealed phases. The propertieswere derived from spatially resolved observations and therefore predominantly obtained with interferometric means,either in the radio/(sub)millimeter or in the optical/infrared wavelength regions. We make summaries and comparisonsof the physical properties, kinematics, and dynamics of these circumstellar structures and delineate trends wherepossible. Amongst others, we report on a quadratic trend of mass accretion rates with mass from TTauri stars to thehighest mass young stellar objects and on the systematic difference in mass infall and accretion rates.


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http://xxx.lanl.gov/pdf/1509.08716.pdf


Filament Fragmentation in High-Mass Star Formation

Henrik Beuther1, Sarah Ragan2, Katharine Johnston2, Thomas Henning1, Alvaro Hacar3 and JouniKainulainen1

1 Max Planck Institute for Astronomy, Konigstuhl 17, 69117 Heidelberg, Germany2 University of Leeds, Leeds, LS2 9JT, UK3 University of Vienna, Turkenschanzstr. 17, A-1180 Vienna, Austria

E-mail contact: beuther at mpia.de

Context: Filamentary structures in the interstellar medium are crucial ingredients in the star formation process. Theyfragment to form individual star-forming cores, and at the same time they may also funnel gas toward the central gascores providing an additional gas reservoir.Aims: We want to resolve the length-scales for filament formation and fragmentation (resolution ≤0.1 pc), in particularthe Jeans length and cylinder fragmentation scale.Methods: We have observed the prototypical high-mass star-forming filament IRDC18223 with the Plateau de BureInterferometer (PdBI) in the 3.2mm continuum and N2H

+(1–0) line emission in a ten field mosaic at a spatial resolutionof ∼ 4′′ (∼14000AU).Results: The dust continuum emission resolves the filament into a chain of at least 12 relatively regularly spaced cores.The mean separation between cores is ∼0.40(±0.18)pc. While this is approximately consistent with the fragmentationof an infinite, isothermal, gravitationally bound gas cylinder, a high mass-to-length ratio of M/l ≈ 1000M⊙ pc−1

requires additional turbulent and/or magnetic support against radial collapse of the filament. The N2H+(1 − 0)

data reveal a velocity gradient perpendicular to the main filament. Although rotation of the filament cannot beexcluded, the data are also consistent with the main filament being comprised of several velocity-coherent sub-filaments.Furthermore, this velocity gradient perpendicular to the filament resembles recent results toward Serpens south thatare interpreted as signatures of filament formation within magnetized and turbulent sheet-like structures. Lower-density gas tracers ([CI] and C18O) reveal a similar red/blueshifted velocity structure on scales around 60′′ east andwest of the IRDC18223 filament. This may tentatively be interpreted as a signature of the large-scale cloud andthe smaller-scale filament being kinematically coupled. We do not identify a velocity gradient along the axis of thefilament. This may either be due to no significant gas flows along the filamentary axis, but it may partly also be causedby a low inclination angle of the filament with respect to the plane of the sky that could minimize such signature.Conclusions: The IRDC18223 3.2mm continuum data are consistent with thermal fragmentation of a gravitationallybound and compressible gas cylinder. However, the large mass-to-length ratio requires additional support – likelyturbulence and/or magnetic fields – against collapse. The N2H

+ spectral line data indicate a kinematic origin ofthe filament, but we cannot conclusively differentiate whether it has formed out of (pre-existing) velocity-coherentsub-filaments and/or whether magnetized converging gas flows, a larger-scale collapsing cloud or even rotation playeda significant role during filament formation.

Accepted by Astronomy & Astrophysics

http://www.mpia.de/homes/beuther/papers.html

Protostellar spin-down: a planetary lift?

Jerome Bouvier1 and David Cebron2

1 Universite Grenoble Alpes, CNRS, IPAG, F-38000 Grenoble, France2 Universite Grenoble Alpes, CNRS, ISTerre, F-38000 Grenoble, France

E-mail contact: Jerome.Bouvier at obs.ujf-grenoble.fr

When they first appear in the HR diagram, young stars rotate at a mere 10% of their break-up velocity. They musthave lost most of the angular momentum initially contained in the parental cloud, the so-called angular momentumproblem. We investigate here a new mechanism by which large amounts of angular momentum might be shed fromyoung stellar systems, thus yielding slowly rotating young stars. Assuming that planets promptly form in circumstellardisks and rapidly migrate close to the central star, we investigate how the tidal and magnetic interactions betweenthe protostar, its close-in planet(s), and the inner circumstellar disk can efficiently remove angular momentum fromthe central object. We find that neither the tidal torque nor the variety of magnetic torques acting between the starand the embedded planet are able to counteract the spin up torques due to accretion and contraction. Indeed, the

13

http://www.mpia.de/homes/beuther/papers.html

former are orders of magnitude weaker than the latter beyond the corotation radius and are thus unable to prevent theyoung star from spinning up. We conclude that star-planet interaction in the early phases of stellar evolution does notappear as a viable alternative to magnetic star-disk coupling to understand the origin of the low angular momentumcontent of young stars.

Accepted by MNRAS


Near-Infrared Spectroscopy of 2M0441+2301 AabBab: A Quadruple System Spanningthe Stellar to Planetary Mass Regimes

Brendan P. Bowler1 and Lynne A. Hillenbrand1

1 California Institute of Technology, 1200 E. California Blvd., Pasadena, CA 91125, USA

E-mail contact: bpbowler at caltech.edu

We present Keck/NIRC2 and OSIRIS near-infrared imaging and spectroscopy of 2M0441+2301 AabBab, a young (1–3Myr) hierarchical quadruple system comprising a low-mass star, two brown dwarfs, and a planetary-mass companionin Taurus. All four components show spectroscopic signs of low surface gravity, and both 2M0441+2301 Aa and Abpossess Paβ emission indicating they each harbor accretion subdisks. Astrometry spanning 2008–2014 reveals orbitalmotion in both the Aab (0.′′23 separation) and Bab (0.′′095 separation) pairs, although the implied orbital periods of>300 years means dynamical masses will not be possible in the near future. The faintest component (2M0441+2301Bb) has an angular H-band shape, strong molecular absorption (VO, CO, H2O, and FeH), and shallow alkali lines,confirming its young age, late spectral type (L1±1), and low temperature (≈1800 K). With individual masses of200+100

−50 Mjup, 35±5 Mjup, 19±3 Mjup, and 9.8±1.8 Mjup, 2M0441+2301 AabBab is the lowest-mass quadruple systemknown. Its hierarchical orbital architecture and mass ratios imply that it formed from the collapse and fragmentationof a molecular cloud core, demonstrating that planetary-mass companions can originate from a stellar-like pathwayanalogous to higher-mass quadruple star systems as first speculated by Todorov et al. More generally, cloud fragmen-tation may be an important formation pathway for the massive exoplanets that are now regularly being imaged onwide orbits.

Accepted by ApJL (811:L30)

http://iopscience.iop.org/article/10.1088/2041-8205/811/2/L30

Compositional evolution during rocky protoplanet accretion

Philip J. Carter1, Zoe M. Leinhardt1, Tim Elliott2, Michael J. Walter2, and Sarah T. Stewart3

1 School of Physics, University of Bristol, H. H. Wills Physics Laboratory, Tyndall Avenue, Bristol BS8 1TL, UK2 School of Earth Sciences, University of Bristol, Wills Memorial Building, Queen?s Road, Bristol BS8 1RJ, UK3 Department of Earth and Planetary Sciences, University of California, One Shields Avenue, Davis, CA 95616, USA

E-mail contact: p.carter at bristol.ac.uk

The Earth appears non-chondritic in its abundances of refractory lithophile elements, posing a significant problemfor our understanding of its formation and evolution. It has been suggested that this non-chondritic compositionmay be explained by collisional erosion of differentiated planetesimals of originally chondritic composition. In thiswork, we present N-body simulations of terrestrial planet formation that track the growth of planetary embryosfrom planetesimals. We simulate evolution through the runaway and oligarchic growth phases under the Grand Tackmodel and in the absence of giant planets. These simulations include a state-of-the-art collision model which allowsmultiple collision outcomes, such as accretion, erosion, and bouncing events, that enables tracking of the evolving coremass fraction of accreting planetesimals. We show that the embryos grown during this intermediate stage of planetformation exhibit a range of core mass fractions, and that with significant dynamical excitation, enough mantle canbe stripped from growing embryos to account for the Earth’s non-chondritic Fe/Mg ratio. We also find that there is alarge diversity in the composition of remnant planetesimals, with both iron-rich and silicate-rich fragments producedvia collisions.

Accepted by ApJ


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http://iopscience.iop.org/article/10.1088/2041-8205/811/2/L30


Discovery of Young Methane Dwarfs in the ρ Ophiuchi L 1688 Dark Cloud

Poshih Chiang1 and W. P. Chen1

1 Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, Zhongli 32001, Taiwan

E-mail contact: pschiang at gmail.com

We report the discovery of two methane dwarfs in the dark cloud L 1688 of the ρ Oph star-forming region. The twoobjects were among the T dwarf candidates with possible methane absorption and cool atmospheres, as diagnosedby infrared colors using deep WIRCam/CFHT HK plus CH4ON images, and IRAC/Spitzer c2d data. Follow-upspectroscopic observations with the FLAMINGOS-2/Gemini South confirmed the methane absorption at 1.6 µm.Compared with spectral templates of known T dwarfs in the field, i.e., of the old populations, Oph J162738−245240(Oph-T3) is a T0/T1 type, whereas Oph J162645−241949 (Oph-T17) is consistent with a T3/T4 type in the H bandbut an L8/T1 in the K band. Compared with the BT-Settl model, both Oph-T3 and Oph-T17 are consistent withbeing cool, ∼1000 K and ∼900 K, respectively, and of low surface gravity, log(g) = 3.5. With an age no more thana couple Myr, these two methane dwarfs thereby represent the youngest T dwarfs ever confirmed. A young late Ldwarf, OphJ162651−242110, was found serendipitously in our spectroscopic observations.

Accepted by ApJL


Could Jupiter or Saturn Have Ejected a Fifth Giant Planet?

Ryan Cloutier1,2, Daniel Tamayo2,3, and Diana Valencia2,1

1 Dept. of Astronomy & Astrophysics University of Toronto, 50 St. George Street, Toronto, Ontario, Canada, M5S3H42 Centre for Planetary Sciences, University of Toronto, Department of Physical & Environmental Sciences, 1265Military Trail, Toronto, Ontario, Canada, M1C 1A43 Canadian Institute for Theoretical Astrophysics, 60 St. George Street, Toronto, Ontario, Canada, M5S 3H8

E-mail contact: cloutier at astro.utoronto.ca

Models of the dynamical evolution of the early solar system following the dispersal of the gaseous protoplanetarydisk have been widely successful in reconstructing the current orbital configuration of the giant planets. Statistically,some of the most successful dynamical evolution simulations have initially included a hypothetical fifth giant planet,of ice giant mass, which gets ejected by a gas giant during the early solar system’s proposed instability phase. Weinvestigate the likelihood of an ice giant ejection event by either Jupiter or Saturn through constraints imposed bythe current orbits of their wide-separation regular satellites Callisto and Iapetus respectively. We show that planetaryencounters that are sufficient to eject an ice giant, often provide excessive perturbations to the orbits of Callisto andIapetus making it difficult to reconcile a planet ejection event with the current orbit of either satellite. Quantitatively,we compute the likelihood of reconciling a regular Jovian satellite orbit with the current orbit of Callisto following anice giant ejection by Jupiter of ∼42% and conclude that such a large likelihood supports the hypothesis of a fifth giantplanet’s existence. A similar calculation for Iapetus reveals that it is much more difficult for Saturn to have ejected anice giant and reconcile a Kronian satellite orbit with that of Iapetus (likelihood ∼1%), although uncertainties regardingthe formation of Iapetus, on its unusual orbit, complicates the interpretation of this result.

Accepted by ApJ


Orbital motions and light curves of young binaries XZ Tau and VY Tau

A.V. Dodin1, N.V. Emelyanov1, A.V. Zharova1, S.A. Lamzin1, E.V. Malogolovets2 and J.M. Roe3

1 Sternberg Astronomical Institute, Moscow State University, Universitetskij pr., 13, 119992 Moscow, Russia2 Special Astrophysical Observatory, N. Arkhyz, Karachai-Cherkesia 369167, Russia3 AAVSO, PO Box 174, Bourbon, MO 65441, USA

E-mail contact: lamzin at sai.msu.ru

15



The results of our speckle interferometric observations of young binaries VY Tau and XZ Tau are presented. For thefirst time, we found a relative displacement of VY Tau components as well as a preliminary orbit for XZ Tau. Itappeared that the orbit is appreciably non-circular and is inclined by i < 47o from the plane of the sky. It meansthat the rotation axis of XZ Tau A and the axis of its jet are significantly non-perpendicular to the orbital plane.We found that the average brightness of XZ Tau had been increasing from the beginning of the last century up tothe mid-thirties and then it decreased by ∆B > 2 mag. The maximal brightness has been reached significantly lateron the time of periastron passage. The total brightness of XZ Tau’s components varied in a non-regular way from1970 to 1985 when eruptions of hot gas from XZ Tau A presumably had occurred. In the early nineties the variationsbecame regular following which a chaotic variability had renewed. We also report that a flare activity of VY Tau hasresumed after 40 yr pause, parameters of the previous and new flares are similar, and the flares are related with theA component.

Accepted by Astronomy Letters


Magnetic activity and hot Jupiters of young Suns: the weak-line T Tauri stars V819Tau and V830 Tau

J.-F. Donati1,2, E. Hebrard1,2, G.A.J. Hussain3,1, C. Moutou4, L. Malo4, K. Grankin5, A.A. Vidotto6,S.H.P. Alencar7, S.G. Gregory8, M.M. Jardine8, G. Herczeg9, J. Morin10, R. Fares11, F. Menard12, J.Bouvier13,14, X. Delfosse13,14, R. Doyon15, M. Takami16, P. Figueira17, P. Petit1,2, I. Boisse18,19 and theMaTYSSE collaboration

1 Universite de Toulouse, UPS-OMP, IRAP, 14 avenue E. Belin, Toulouse, F–31400 France2 CNRS, IRAP / UMR 5277, Toulouse, 14 avenue E. Belin, F–31400 France3 ESO, Karl-Schwarzschild-Str. 2, D-85748 Garching, Germany4 CFHT Corporation, 65-1238 Mamalahoa Hwy, Kamuela, Hawaii 96743, USA5 Crimean Astrophysical Observatory, Nauchny, Crimea 2984096 Observatoire de Geneve, Chemin des Maillettes 51, CH-1290 Versoix, Switzerland7 Departamento de Fısica – ICEx – UFMG, Av. Antonio Carlos, 6627, 30270-901 Belo Horizonte, MG, Brazil8 SUPA, School of Physics and Astronomy, Univ. of St Andrews, St Andrews, Scotland KY16 9SS, UK9 Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Haidian Qu, Beijing 100871,China10 LUPM, Universite de Montpellier, CNRS, place E. Bataillon, F–34095 Montpellier, France11 INAF - Osservatorio Astrofisico di Catania, via S. Sofia 78, I–95123 Catania, Italy12 CNRS, UMI-FCA / UMI 3386, France, and Universidad de Chile, Santiago, Chile13 Universite Grenoble Alpes, IPAG, BP 53, F–38041 Grenoble Cedex 09, France14 CNRS, IPAG / UMR 5274, BP 53, F–38041 Grenoble Cedex 09, France15 Departement de physique, Universite de Montreal, C.P. 6128, Succursale Centre-Ville, Montreal, QC, Canada H3C3J716 Institute of Astronomy and Astrophysics, Academia Sinica, PO Box 23-141, 106, Taipei, Taiwan17 Centro de Astrofısica, Universidade do Porto, Rua das Estrelas, 4150-762 Porto, Portugal18 Universite Aix-Marseille, LAM, F–13388 Marseille, France19 CNRS, LAM / UMR 7326, F–13388 Marseille, France

E-mail contact: jean-francois.donati at irap.omp.eu

We report results of a spectropolarimetric and photometric monitoring of the weak-line T Tauri stars (wTTSs) V819Tau and V830 Tau within the MaTYSSE programme, involving the ESPaDOnS spectropolarimeter at the Canada-France-Hawaii Telescope. At ∼3 Myr, both stars dissipated their discs recently and are interesting objects for probingstar and planet formation. Profile distortions and Zeeman signatures are detected in the unpolarized and circularly-polarized lines, whose rotational modulation we modelled using tomographic imaging, yielding brightness and magneticmaps for both stars.We find that the large-scale magnetic fields of V819 Tau and V830 Tau are mostly poloidal and can be approximatedat large radii by 350–400 G dipoles tilted at ∼30◦ to the rotation axis. They are significantly weaker than the fieldof GQ Lup, an accreting classical T Tauri star (cTTS) with similar mass and age which can be used to compare

16


the magnetic properties of wTTSs and cTTSs. The reconstructed brightness maps of both stars include cool spotsand warm plages. Surface differential rotation is small, typically ∼4.4 × smaller than on the Sun, in agreement withprevious results on wTTSs.Using our Doppler images to model the activity jitter and filter it out from the radial velocity (RV) curves, we obtainRV residuals with dispersions of 0.033 and 0.104 km s−1 for V819 Tau and V830 Tau respectively. RV residuals suggestthat a hot Jupiter may be orbiting V830 Tau, though additional data are needed to confirm this preliminary result.We find no evidence for close-in giant planet around V819 Tau.

Accepted by MNRAS


The young cluster NGC 2282 : a multi-wavelength perspective

Somnath Dutta1, S. Mondal1, J. Jose2, R. K. Das1, M. R. Samal3 and S. Ghosh1

1 S. N. Bose National Centre for Basic Sciences, Block-JD, Sector-III, Salt Lake, Kolkata-700098, India2 Kavli Institute for Astronomy and Astrophysics,Peking University, Yi He Yuan Lu 5, Haidian District, Beijing100871, China3 Aix Marseille Universite, CNRS, LAM (Laboratoire d’Astrophysique de Marseille) UMR 7326, 13388 Marseille,France

E-mail contact: somnath12 at boson.bose.res.in

We present the analysis of the stellar content of NGC 2282, a young cluster in the Monoceros constellation, usingdeep optical BV I and IPHAS photometry along with infrared (IR) data from UKIDSS and Spitzer-IRAC. Based onthe stellar surface density analysis using nearest neighborhood method, the radius of the cluster is estimated as ∼3.15 arcmin. From optical spectroscopic analysis of 8 bright sources, we have classified three early B-type membersin the cluster, which includes, HD 289120, a previously known B2 V type star, a Herbig Ae/Be star (B0.5 Ve) anda B5 V star. From spectrophotometric analyses, the distance to the cluster has been estimated as ∼ 1.65 kpc. TheK-band extinction map is estimated using nearest neighborhood technique, and the mean extinction within the clusterarea is found to be AV ∼ 3.9 mag. Using IR colour-colour criteria and Hα-emission properties, we have identified atotal of 152 candidate young stellar objects (YSOs) in the region, of which, 75 are classified as Class II, 9 are Class IYSOs. Our YSO catalog also includes 50 Hα-emission line sources, identified using slitless spectroscopy and IPHASphotometry data. Based on the optical and near-IR colour-magnitude diagram analyses, the cluster age has beenestimated to be in the range of 2 − 5 Myr, which is in agreement with the estimated age from disc fraction (∼ 58%).Masses of these YSOs are found to be ∼ 0.1−2.0 M⊙. Spatial distribution of the candidate YSOs shows sphericalmorphology, more or less similar to the surface density map.

Accepted by MNRAS

http://arxiv.org/pdf/1509.08594v1.pdf

Radio monitoring of the periodically variable IR source LRLL 54361: No direct corre-lation between the radio and IR emissions

Jan Forbrich1,2, Luis F. Rodrıguez3, Aina Palau3, Luis A. Zapata3, James Muzerolle4 and Robert A.Gutermuth5

1 University of Vienna, Department of Astrophysics, Turkenschanzstraße 17, 1180 Vienna, Austria2 Harvard-Smithsonian Center for Astrophysics, 60 Garden St MS 72, Cambridge, MA 02138, USA3 Instituto de Radioastronomıa y Astrofısica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacan, Mexico4 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA5 Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA

E-mail contact: jan.forbrich at univie.ac.at

LRLL 54361 is an infrared source located in the star forming region IC 348 SW. Remarkably, its infrared luminosityincreases by a factor of 10 during roughly one week every 25.34 days. To understand the origin of these remarkableperiodic variations, we obtained sensitive 3.3 cm JVLA radio continuum observations of LRLL 54361 and its surround-ings in six different epochs: three of them during the IR-on state and three during the IR-off state. The radio source

17



associated with LRLL 54361 remained steady and did not show a correlation with the IR variations. We suggest thatthe IR is tracing the results of fast (with a timescale of days) pulsed accretion from an unseen binary companion,while the radio traces an ionized outflow with an extent of ∼100 AU that smooths out the variability over a period oforder a year. The average flux density measured in these 2014 observations, 27±5 µJy, is about a factor of two lessthan that measured about 1.5 years before, 53±11 µJy, suggesting that variability in the radio is present, but overlarger timescales than in the IR. We discuss other sources in the field, in particular two infrared/X-ray stars that showrapidly varying gyrosynchrotron emission.

Accepted by The Astrophysical Journal


Squeezed between shells? On the origin of the Lupus I molecular cloud.APEX/LABOCA, Herschel, and Planck observations

B. Gaczkowski1, T. Preibisch1, T. Stanke2, M.G.H. Krause1,3,4, A. Burkert1,3, R. Diehl3,4, K. Fierlinger1,4,D. Kroell1,3, J. Ngoumou1 and V. Roccatagliata1

1 Universitats-Sternwarte Munchen, Ludwig-Maximilians-Universitat, Scheinerstr. 1, 81679 Munchen, Germany2 ESO, Karl-Schwarzschild-Strasse 2, 85748 Garching bei Munchen, Germany3 Max-Planck-Institut fur extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany4 Excellence Cluster Universe, Technische Universitat Munchen, Boltzmannstrasse 2, 85748 Garching, Germany

E-mail contact: bengac at usm.uni-muenchen.de

The Lupus I cloud is found between the Upper-Scorpius (USco) and the Upper-Centaurus-Lupus (UCL) sub-groups ofthe Scorpius-Centaurus OB-association, where the expanding USco H I shell appears to interact with a bubble currentlydriven by the winds of the remaining B-stars of UCL. We want to study how collisions of large-scale interstellar gasflows form and influence new dense clouds in the ISM. We performed LABOCA continuum sub-mm observations ofLupus I that provide for the first time a direct view of the densest, coldest cloud clumps and cores at high angularresolution. We complemented those by Herschel and Planck data from which we constructed column density andtemperature maps. From the Herschel and LABOCA column density maps we calculated PDFs to characterizethe density structure of the cloud. The northern part of Lupus I is found to have on average lower densities andhigher temperatures as well as no active star formation. The center-south part harbors dozens of pre-stellar coreswhere density and temperature reach their maximum and minimum, respectively. Our analysis of the column densityPDFs from the Herschel data show double peak profiles for all parts of the cloud which we attribute to an externalcompression. In those parts with active star formation, the PDF shows a power-law tail at high densities. The PDFswe calculated from our LABOCA data trace the denser parts of the cloud showing one peak and a power-law tail.With LABOCA we find 15 cores with masses between 0.07 and 1.71M⊙ and a total mass of ≈ 8M⊙. The total gasand dust mass of the cloud is ≈ 164M⊙ and hence ∼ 5% of the mass is in cores. From the Herschel and Planckdata we find a total mass of ≈ 174M⊙ and ≈ 171M⊙, respectively. The position, orientation and elongated shapeof Lupus I, the double peak PDFs and the population of pre-stellar and protostellar cores could be explained by thelarge-scale compression from the advancing USco H I shell and the UCL wind bubble.

Accepted by A&A


Dense gas in the Galactic central molecular zone is warm and heated by turbulence

Adam Ginsburg1, Christian Henkel2,3, Yiping Ao4,5, Denise Riquelme2, Jens Kauffmann2, ThusharaPillai2, Elisabeth A.C. Mills6, Miguel A. Requena-Torres2, Katharina Immer1, Leonardo Testi1, Juer-gen Ott6, John Bally7, Cara Battersby8, Jeremy Darling7, Susanne Aalto9, Thomas Stanke1, SarahKendrew10, J.M. Diederik Kruijssen11, Steven Longmore12, James Dale13, Rolf Guesten2, Karl M.Menten2

1European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei Muenchen, Germany2Max Planck Institute for Radio Astronomy, auf dem Hugel, Bonn3Astron. Dept., King Abdulaziz University, P.O. Box 80203, Jeddah 21589, Saudi Arabia

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4National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan5Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008, China6National Radio Astronomy Observatory, Socorro7CASA, University of Colorado, 389-UCB, Boulder, CO 80309, USA8Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA9Department of Earth and Space Sciences, Chalmers University of Technology, Sweden10Department of Astrophysics, The Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK 11Max-PlanckInstitut fur Astrophysik, Karl-Schwarzschild-Straße 1, 85748 Garching, Germany12Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill,Liverpool L3 5RF, United Kingdom13University Observatory Munich, Scheinerstr. 1, D-81679 Munchen, Germany

E-mail contact: [email protected]

The Galactic center is the closest region in which we can study star formation under extreme physical conditions likethose in high-redshift galaxies. We measure the temperature of the dense gas in the central molecular zone (CMZ)and examine what drives it. We mapped the inner 300 pc of the CMZ in the temperature-sensitive J = 3 − 2 para-formaldehyde (p-H2CO) transitions. We used the 32,1–22,0 / 30,3–20,2 line ratio to determine the gas temperature inn ∼ 104 − 105 cm−3 gas. We have produced temperature maps and cubes with 30 arcsec and 1 km/s resolution andpublished all data in FITS form. Dense gas temperatures in the Galactic center range from ∼ 60 K to > 100 K inselected regions. The highest gas temperatures TG > 100 K are observed around the Sgr B2 cores, in the extended SgrB2 cloud, the 20 km/s and 50 km/s clouds, and in “The Brick” (G0.253+0.016). We infer an upper limit on the cosmicray ionization rate ζCR < 10−14 s−1. The dense molecular gas temperature of the region around our Galactic center issimilar to values found in the central regions of other galaxies, in particular starburst systems. The gas temperature isuniformly higher than the dust temperature, confirming that dust is a coolant in the dense gas. Turbulent heating canreadily explain the observed temperatures given the observed line widths. Cosmic rays cannot explain the observedvariation in gas temperatures, so CMZ dense gas temperatures are not dominated by cosmic ray heating. The gastemperatures previously observed to be high in the inner ∼ 75 pc are confirmed to be high in the entire CMZ.

Accepted by A&A


The data can be accessed from doi:10.7910/DVN/27601 and are available from CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/

ALMA images of discs: are all gaps carved by planets?

J.-F. Gonzalez1, G. Laibe2, S.T. Maddison3, C. Pinte4,5, and F. Menard4,5

1 Universite de Lyon, Lyon, F-69003, France; Universite Lyon 1, Observatoire de Lyon, 9 avenue Charles Andre,Saint-Genis Laval, F-69230, France; CNRS, UMR 5574, Centre de Recherche Astrophysique de Lyon ; Ecole NormaleSuprieure de Lyon, Lyon, F-69007, France2 School of Physics and Astronomy, University of Saint Andrews, North Haugh, St Andrews, Fife KY16 9SS, UnitedKingdom3 Centre for Astrophysics and Supercomputing, Swinburne University of Technology, PO Box 218, Hawthorn, VIC3122, Australia4 UMI-FCA, CNRS/INSU France (UMI 3386), and Departamento de Astronomıa, Universidad de Chile, Casilla 36-DSantiago, Chile5 UJF-Grenoble 1 / CNRS-INSU, Institut de Planetologie et d?Astrophysique de Grenoble, UMR 5274, Grenoble,F-38041, France

E-mail contact: jean-francois.gonzalez at ens-lyon.fr

Protoplanetary discs are now routinely observed and exoplanets, after the numerous indirect discoveries, are startingto be directly imaged. To better understand the planet formation process, the next step is the detection of formingplanets or of signposts of young planets still in their disc, such as gaps. A spectacular example is the ALMA scienceverification image of HL Tau showing numerous gaps and rings in its disc. To study the observability of planet gaps,we ran 3D hydrodynamical simulations of a gas and dust disc containing a 5 MJ gap-opening planet and characterised

19


http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/

the spatial distribution of migrating, growing and fragmenting dust grains. We then computed the correspondingsynthetic images for ALMA. For a value of the dust fragmentation threshold of 15 m s−1 for the collisional velocity, weidentify for the first time a self-induced dust pile up in simulations taking fragmentation into account. This feature,in addition to the easily detected planet gap, causes a second apparent gap that could be mistaken for the signatureof a second planet. It is therefore essential to be cautious in the interpretation of gap detections.

Accepted by MNRAS Letters


Possible smoking-gun evidence for initial mass segregation in re-virialized post-gas ex-pulsion globular clusters

Hosein Haghi1, Akram Hasani Zonoozi1, Pavel Kroupa2, Sambaran Banerjee2,3 and Holger Baumgardt4

1 Institute for Advanced Studies in Basic Sciences (IASBS), P.O. Box 11365-9161, Zanjan, Iran2 Helmholtz-Institut fur Strahlen-und Kernphysik (HISKP), Universitat Bonn, Rheinische Friedrich-Wilhelms-UniversitatNussallee 14-16 D-53115 Bonn Germany3 Argelander Institute fur Astronomie (AIfA), Auf dem Hugel 71, 53121 Bonn, Germany4 University of Queensland, School of Mathematics and Physics, Brisbane, QLD 4072, Australia

E-mail contact: haghi at iasbs.ac.ir

We perform a series of direct N -body calculations to investigate the effect of residual gas expulsion from the gas-embedded progenitors of present-day globular clusters (GCs) on the stellar mass function (MF). Our models starteither tidally filling or underfilling, and either with or without primordial mass segregation. We cover 100 Myr of theevolution of modeled clusters and show that the expulsion of residual gas from initially mass-segregated clusters leads toa significantly shallower slope of the stellar MF in the low- (m ≤ 0.50M⊙) and intermediate-mass (≃ 0.50− 0.85M⊙)regime. Therefore, the imprint of residual gas expulsion and primordial mass segregation might be visible in thepresent-day MF. We find that the strength of the external tidal field, as an essential parameter, influences the degreeof flattening, such that a primordially mass-segregated tidally-filling cluster with rh/rt ≥ 0.1 shows a strongly depletedMF in the intermediate stellar mass range. Therefore, the shape of the present-day stellar MF in this mass rangeprobes the birth place of clusters in the Galactic environment. We furthermore find that this flattening agrees withthe observed correlation between the concentration of a cluster and its MF slope, as found by de Marchi et al.. Weshow that if the expansion through the residual gas expulsion in primordial mass segregated clusters is the reason forthis correlation then GCs most probably formed in strongly fluctuating local tidal fields in the early proto-Milky Waypotential, supporting the recent conclusion by Marks & Kroupa.

Accepted by MNRAS


The Early ALMA View of the FU Ori Outburst System

A.S. Hales1,2, S.A. Corder1,2, W.R.D. Dent1,3, S.M. Andrews4, J.A. Eisner5 and L.A. Cieza6,7

1 Atacama Large Millimeter/Submillimeter Array, Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura 763-0355, Santiago - Chile62 National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, Virginia, 22903-2475, United States3 European Southern Observatory, Karl-Schwarzschild-Str. 2, 85748, Garching bei Munchen, Germany4 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, United States5 Steward Observatory, University of Arizona, 933 N Cherry Ave., Tucson, AZ 85721, United States6 Nucleo de Astronomıa, Facultad de Ingenierıa, Universidad Diego Portales, Chile7 Millenium Nucleus, Protoplanetary Disks in ALMA Early Science, Chile

E-mail contact: ahales at alma.cl

We have obtained ALMA Band 7 observations of the FU Ori outburst system at 0.′′6 × 0.′′5 resolution to measure thelink between the inner disk instability and the outer disk through sub-mm continuum and molecular line observations.Our observations detect continuum emission which can be well modeled by two unresolved sources located at theposition of each binary component. The interferometric observations recover the entire flux reported in previous

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single-dish studies, ruling out the presence of a large envelope. Assuming that the dust is optically thin, we derive diskdust masses of 2 × 10−4 M⊙ and 8 × 10−5 M⊙, for the north and south components respectively. We place limits onthe disks’ radii of r < 45 AU. We report the detection of molecular emission from 12CO(3–2), HCO+(4–3) and fromHCN(4–3). The 12CO appears widespread across the two binary components, and is slightly more extended than thecontinuum emission. The denser gas tracer HCO+ peaks close to the position of the southern binary component, whileHCN appears peaked at the position of the northern component. This suggests that the southern binary component isembedded in denser molecular material, consistent with previous studies that indicate a heavily reddened object. Atthis angular resolution any interaction between the two unresolved disk components cannot be disentangled. Higherresolution images are vital to understanding the process of star formation via rapid accretion FU Ori-type episodes.

Accepted by ApJ


The Evolution of Inner Disk Gas in Transition Disks

K. Hoadley1,2, K. France1,2, R.D. Alexander3, M. McJunkin1,2, and P.C. Schneider4

1 Laboratory for Atmospheric and Space Physics, University of Colorado, Boulder, CO 80303-7814, USA2 Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0389, USA3 Department of Physics & Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK4 ESTEC/ESA, Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands

E-mail contact: keri.hoadley at colorado.edu

Investigating the molecular gas in the inner regions of protoplanetary disks provides insight into how the moleculardisk environment changes during the transition from primordial to debris disk systems. We conduct a small survey ofmolecular hydrogen (H2) fluorescent emission, using 14 well-studied Classical T Tauri stars at two distinct dust diskevolutionary stages, to explore how the structure of the inner molecular disk changes as the optically thick warm dustdissipates. We simulate the observed HI-Lyman α-pumped H2 disk fluorescence by creating a 2D radiative transfermodel that describes the radial distributions of H2 emission in the disk atmosphere and compare these to observationsfrom the Hubble Space Telescope. We find the radial distributions that best describe the observed H2 FUV emissionarising in primordial disk targets (full dust disk) are demonstrably different than those of transition disks (little-to-nowarm dust observed). For each best-fit model, we estimate inner and outer disk emission boundaries (rin and rout),describing where the bulk of the observed H2 emission arises in each disk, and we examine correlations between theseand several observational disk evolution indicators, such as n13−31, rin,CO, and the mass accretion rate. We find strong,positive correlations between the H2 radial distributions and the slope of the dust SED, implying the behavior of themolecular disk atmosphere changes as the inner dust clears in evolving protoplanetary disks. Overall, we find that H2

inner radii are ∼4 times larger in transition systems, while the bulk of the H2 emission originates inside the dust gapradius for all transitional sources.

Accepted by ApJ


Periodic Accretion Instabilities in the Protostar L1634 IRS 7

Klaus W. Hodapp1 and Rolf Chini2

1 University of Hawaii, Institute for Astronomy, 640 N. Aohoku Place, Hilo, HI 96720, USA2 Ruhr-Universitaet Bochum, Astronomisches Institut, Universitaetsstrasse 15, D-44801 Bochum, Germany

E-mail contact: hodapp at ifa.hawaii.edu

The small molecular cloud Lynds 1634 contains at least three outflow sources. We found one of these, IRS 7, to bevariable with a period of 37.14 ± 0.04 days and an amplitude of approximately 2 mag in the Ks band. The lightcurve consists of a quiescent phase with little or no variation, and a rapid outburst phase. During the outburst phase,the rapid brightness variation generates light echoes that propagate into the surrounding molecular cloud, allowinga measurement of the distance to IRS 7 of 404 pc ± 35 pc. We observed only a marginally significant change inthe H − K color during the outburst phase. The K-band spectrum of IRS 7 shows CO bandhead emission but itsequivalent width does not change significantly with the phase of the light curve. The H2 1–0 S(1) line emission does

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not follow the variability of the continuum flux. We also used the imaging data for a proper motion study of theoutflows originating from the IRS 7 and the FIR source IRAS 05173-0555, and confirm that these are indeed distinctoutflows.



The Arches Cluster: Extended Structure and Tidal Radius

Matthew W. Hosek Jr.1, Jessica R. Lu1, Jay Anderson2, Andrea M. Ghez3, Mark R. Morris3 andWilliam I. Clarkson4

1 Institute for Astronomy, University of Hawaii, USA2 Space Telescope Science Institute, USA3 UCLA, USA4 University of Michigan-Dearborn, USA

E-mail contact: mwhosek at hawaii.edu

At a projected distance of ∼26 pc from Sgr A*, the Arches cluster provides insight to star formation in the extremeGalactic Center (GC) environment. Despite its importance, many key properties such as the cluster’s internal structureand orbital history are not well known. We present an astrometric and photometric study of the outer region of theArches cluster (R > 6.25”) using HST WFC3IR. Using proper motions we calculate membership probabilities forstars down to F153M = 20 mag (∼2.5 M⊙) over a 120” x 120” field of view, an area 144 times larger than previousastrometric studies of the cluster. We construct the radial profile of the Arches to a radius of 75” (∼3 pc at 8 kpc),which can be well described by a single power law. From this profile we place a 3σ lower limit of 2.8 pc on the observedtidal radius, which is larger than the predicted tidal radius (1 – 2.5 pc). Evidence of mass segregation is observedthroughout the cluster and no tidal tail structures are apparent along the orbital path. The absence of breaks in theprofile suggests that the Arches has not likely experienced its closest approach to the GC between ∼0.2 – 1 Myr ago.If accurate, this constraint indicates that the cluster is on a prograde orbit and is located front of the sky plane thatintersects Sgr A*. However, further simulations of clusters in the GC potential are required to interpret the observedprofile with more confidence.

Accepted by ApJ


A Keplerian-like disk around the forming O-type star AFGL 4176

Katharine G. Johnston1, Thomas P. Robitaille2, Henrik Beuther2, Hendrik Linz2, Paul Boley3, RolfKuiper4,2, Eric Keto5, Melvin G. Hoare1 and Roy van Boekel2

1 School of Physics & Astronomy, E.C. Stoner Building, The University of Leeds, Leeds, LS2 9JT, UK2 Max Planck Institute for Astronomy, Konigstuhl 17, D-69117 Heidelberg, Germany3 Ural Federal University, Astronomical Observatory, 51 pr. Lenina, Ekaterinburg, Russia4 Institute of Astronomy and Astrophysics, Eberhard Karls University Tubingen, Auf der Morgenstelle 10, D-72076Tubingen, Germany5 Harvard-Smithsonian Center for Astrophysics, 60 Garden St, Cambridge, MA 02138, USA

E-mail contact: k.g.johnston at leeds.ac.uk

We present Atacama Large Millimeter/submillimeter Array (ALMA) line and continuum observations at 1.2mm with∼0.3′′ resolution that uncover a Keplerian-like disk around the forming O-type star AFGL4176. The continuumemission from the disk at 1.21mm (source mm1) has a deconvolved size of 870±110AU × 330±300AU and arisesfrom a structure ∼8M⊙ in mass, calculated assuming a dust temperature of 190K. The first-moment maps, pixel-to-pixel line modeling, assuming local thermodynamic equilibrium (LTE), and position-velocity diagrams of the CH3CNJ=13–12 K-line emission all show a velocity gradient along the major axis of the source, coupled with an increasein velocity at small radii, consistent with Keplerian-like rotation. The LTE line modeling shows that where CH3CNJ=13–12 is excited, the temperatures in the disk range from ∼70 to at least 300K and that the H2 column densitypeaks at 2.8×1024 cm−2. In addition, we present Atacama Pathfinder Experiment (APEX) 12CO observations which

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show a large-scale outflow from AFGL4176 perpendicular to the major axis of mm1, supporting the disk interpretation.Finally, we present a radiative transfer model of a Keplerian disk surrounding an O7 star, with a disk mass and radiusof 12M⊙ and 2000AU, that reproduces the line and continuum data, further supporting our conclusion that ourobservations have uncovered a Keplerian disk around an O-type star.

Accepted by the Astrophysical Journal Letters


The past photometric history of the FU Ori-type young eruptive star2MASS J06593158−0405277 = V960 Mon

Rajka Jurdana-vepica1 and Ulisse Munari2

1 Physics Department, University of Rijeka, Radmile Matejvic, 51000, Rijeka, Croatia2 INAF Astronomical Observatory of Padova, via dell’Osservatorio 8, 36012 Asiago (VI), Italy

E-mail contact: ulisse.munari at oapd.inaf.it

The known FU Ori-type young eruptive stars are exceedingly rare (a dozen or so confirmed objects) and 2MASSJ06593158−0405277, with its 2014 outburst, is likely the latest addition to the family. All members have displayedjust one such eruption in their recorded history, an event lasting for decades. To test the FU Ori nature of 2MASSJ06593158−0405277, we have reconstructed its photometric history by measuring its brightness on Harvard photo-graphic plates spanning the time interval 1899–1989. No previous large amplitude eruption similar to that initiatedin 2014 has been found, as in bona fide FU Ori-type objects. The median value of the brightness in quiescence of2MASS J06593158−0405277 is B=15.5, with the time interval 1935–1950 characterized by a large variability (∼1 magamplitude) that contrasts with the remarkable photometric stability displayed at later epochs. The variability during1935–1950 can either be ascribed to some T Tau like activity of 2MASS J06593158−0405277 itself or to the also youngand fainter star 2MASS J06593168−0405224 that lies 5′′ to the north and forms an unresolved pair at the astrometricscale of Harvard photographic plates.

Accepted by New Astronomy


Galactic cold cores VI. Dust opacity spectral index

M. Juvela1, K. Demyk2,3, Y. Doi5, A. Hughes3,2,8, C. Lefevre7, D. J. Marshall9, C. Meny2,3, J.Montillaud4, L. Pagani7, D. Paradis2,3, I. Ristorcelli2,3, J. Malinen1, L. A. Montier2,3, R. Paladini6,V.-M. Pelkonen1 and A. Rivera-Ingraham2,10

1 Department of Physics, P.O.Box 64, FI-00014, University of Helsinki, Finland2 Universite de Toulouse, UPS-OMP, IRAP, F-31028 Toulouse cedex 4, France3 CNRS, IRAP, 9 Av. colonel Roche, BP 44346, F-31028 Toulouse cedex 4, France4 Institut UTINAM, CNRS UMR 6213, OSU THETA, Universite de Franche-Comte, 41 bis avenue de l’Observatoire,25000 Besancon, France5 The University of Tokyo, Komaba 3-8-1, Meguro, Tokyo, 153-8902, Japan6 IPAC, Caltech, Pasadena, USA7 LERMA, CNRS UMR8112, Observatoire de Paris, 61 avenue de l’observatoire 75014 Paris, France8 Max-Planck-Institut fur Astronomie, Knigstuhl 17, D-69117 Heidelberg, Germany9 Laboratoire AIM, IRFU/Service d’Astrophysique - CEA/DSM - CNRS - Universite Paris Diderot, Bt. 709, CEA-Saclay, F-91191, Gif-sur-Yvette Cedex, France10 European Space Astronomy Centre (ESA-ESAC), PO Box 78, 28691, Villanueva de la Caada, Madrid, Spain

E-mail contact: mika.juvela at helsinki.fi

The Galactic Cold Cores project has carried out Herschel photometric observations of 116 fields where the Plancksurvey has found signs of cold dust emission. The fields contain sources in different environments and different phasesof star formation. Previous studies have revealed variations in their dust submillimetre opacity. The aim is to measurethe value of dust opacity spectral index and to understand its variations spatially and with respect to other parameters,such as temperature, column density, and Galactic location. The dust opacity spectral index β and the dust colour

23



temperature T are derived using Herschel and Planck data. The relation between β and T is examined for the wholesample and inside individual fields. Based on IRAS and Planck data, the fields are characterised by a median colourtemperature of 16.1K and a median opacity spectral index of β = 1.84. The values are not correlated with Galacticlongitude. We observe a clear T –β anti-correlation. In Herschel observations, constrained at lower resolution byPlanck data, the variations follow the column density structure and βFIR can rise to ∼ 2.2 in individual clumps. Thehighest values are found in starless clumps. The Planck 217GHz band shows a systematic excess that is not restrictedto cold clumps and is thus consistent with a general flattening of the dust emission spectrum at millimetre wavelengths.When fitted separately below and above 700µm, the median spectral index values are βFIR ∼ 1.91 and β(mm) ∼ 1.66.The spectral index changes as a function of column density and wavelength. The comparison of different data sets andthe examination of possible error sources show that our results are robust. However, β variations are partly maskedby temperature gradients and the changes in the intrinsic grain properties may be even greater.

Accepted by A&A


Fingerprints of giant planets in the atmospheres of Herbig stars

Mihkel Kama1, Colin P. Folsom2,3 and Paola Pinilla1

1 Leiden Observatory, P.O. Box 9513, NL-2300 RA, Leiden, The Netherlands2 Universite de Grenoble Alpes, IPAG, F-38000 Grenoble, France3 CNRS, IPAG, F-38000 Grenoble, France

E-mail contact: mkama at strw.leidenuniv.nl

Around 2% of all A stars have photospheres depleted in refractory elements. This is hypothesised to arise fromgas being accreted more efficiently than dust, but the specific processes and the origin of the material – circum- orinterstellar – are not known. The same depletion is seen in 30% of young, disk-hosting Herbig Ae/Be stars. Weinvestigate whether the chemical peculiarity originates in a circumstellar disk. Using a sample of systems for whichboth the stellar abundances and the protoplanetary disk structure are known, we find that stars hosting warm, flaringgroup I disks typically have Fe, Mg and Si depletions of 0.5 dex compared to the solar-like abundances of stars hostingcold, flat group II disks. The volatile, C and O, abundances in both sets are identical. Group I disks are generallytransitional, having radial cavities depleted in millimetre-sized dust grains, while those of group II are usually not.Thus we propose that the depletion of heavy elements emerges as Jupiter-like planets block the accretion of part ofthe dust, while gas continues to flow towards the central star. We calculate gas to dust ratios for the accreted materialand find values consistent with models of disk clearing by planets. Our results suggest that giant planets of ∼0.1 to10MJup are hiding in at least 30% of Herbig Ae/Be disks.

Accepted by A&A Letters


Spiral-driven accretion in protoplanetary discs - I. 2D models

Geoffroy Lesur1,2, Patrick Hennebelle3, and Sebastien Fromang3

1 Univ. Grenoble Alpes, IPAG, F-38000 Grenoble, France2 CNRS, IPAG, F-38000 Grenoble, France3 Laboratoire AIM, CEA/DSM–CNRS–Universite Paris 7, Irfu/Service d’Astrophysique, CEA-Saclay, 91191 Gif-sur-Yvette, France

E-mail contact: geoffroy.lesur at ujf-grenoble.fr

We numerically investigate the dynamics of a 2D non-magnetised protoplanetary disc surrounded by an inflow comingfrom an external envelope. We find that the accretion shock between the disc and the inflow is unstable, leading tothe generation of large-amplitude spiral density waves. These spiral waves propagate over long distances, down toradii at least ten times smaller than the accretion shock radius. We measure spiral-driven outward angular momentumtransport with 10−4 < α < 10−2 for an inflow accretion rate Minf > 10−8 M⊙ yr−1. We conclude that the interactionof the disc with its envelope leads to long-lived spiral density waves and radial angular momentum transport withrates that cannot be neglected in young non-magnetised protostellar discs.

24





Spectroscopically resolved far-IR observations of the massive star-forming region G5.89–0.39

S. Leurini1, F. Wyrowski1, A. Gusdorf2,3, R. Guesten1, M. Gerin2,3, F. Levrier2,3, H. W. Heubers4,5,K. Jacobs6 and O. Ricken1

1 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, D-53121, Bonn, Germany2 ERMA, Observatoire de Paris, Ecole Normale Superieure, PSL Research University, CNRS, UMR 8112, F-75014,Paris, France3 Sorbonne Universites, UPMC Univ. Paris 6, UMR 8112, LERMA, F-75005, Paris, France4 Deutsches Zentrum fr Luft-und Raumfahrt (DLR), Institute of Optical Sensor Systems, Rutherfordstrasse 2, D-12489, Berlin, Germany5 Humboldt-Universitat zu Berlin, Department of Physics, Newtonstr. 15, 12489 Berlin, Germany6 Kolner Observatorium fur Submm Astronomie (KOSMA), I. Physikalisches Institut, Universitat zu Koln, ZulpicherStr. 77, 50937 Cologne, Germany

E-mail contact: sleurini at mpifr.de

The fine-structure line of atomic oxygen at 63µm ([OI]63µm) is an important diagnostic tool in different fields ofastrophysics: it is for example predicted to be the main coolant in several environments of star-forming regions (SFRs).However, our knowledge of this line relies on observations with low spectral resolution, and the real contribution of eachcomponent (photon-dominated region, jet) in the complex environment of SFRs to its total flux is poorly understood.We investigate the contribution of jet and photon-dominated region emission, and of absorption to the [OI]63µm linetowards the hot gas around the ultra-compact Hii region G5.89–0.39 and study the far-IR line luminosity of the sourcein different velocity regimes through spectroscopically resolved spectra of atomic oxygen, [CII], CO, OH, and H2O.We mapped G5.89–0.39 in [OI]63µm and in CO(16–15) with the GREAT receiver onboard SOFIA. We also observedthe central position of the source in the ground-state OH 2Π3/2, J = 5/2 → J = 3/2 triplet and in the excited OH2Π1/2, J = 3/2 → J = 1/2 triplets with SOFIA. These data were complemented with APEX CO(6–5) and CO(7–6)maps and with Herschel/HIFI maps and single-pointing observations in lines of [CII], H2O, and HF.

The [OI] spectra in G5.89–0.39 are severely contaminated by absorptions from the source envelope and from differentclouds along the line of sight. Emission is detected only at high velocities, and it is clearly associated with thecompact north-south outflows traced by extremely high-velocity emission in low-J CO lines. The mass-loss rateand the energetics of the jet system derived from the [OI]63µm line agree well with previous estimates from CO,thus suggesting that the molecular outflows in G5.89–0.39 are driven by the jet system seen in [OI]. The far-IRline luminosity of G5.89–0.39 is dominated by [OI] at high-velocities; the second coolant in this velocity regime isCO, while [CII], OH and H2O are minor contributors to the total cooling in the outflowing gas. Finally, we deriveabundances of different molecules in the outflow: water has low abundances relative to H2 of 10−8 − 10−6, and OH of10−8. Interestingly, we find an abundance of HF to H2 of 10−8, comparable with measurements in diffuse gas. Ourstudy shows the importance of spectroscopically resolved observations of the [OI]63µm line for using this transition asdiagnostic of star-forming regions. While this was not possible until now, the GREAT receiver onboard SOFIA hasrecently opened the possibility of detailed studies of the [OI]63µm line to investigate the potential of the transition forprobing different environments.

Accepted by Accepted by Astronomy & Astrophysics


Probing the effects of external irradiation on low-mass protostars through unbiased linesurveys

Johan E. Lindberg1,2, Jes K. Jørgensen1, Yoshimasa Watanabe3, Suzanne E. Bisschop1, Nami Sakai3

and Satoshi Yamamoto3

1 Centre for Star and Planet Formation, Niels Bohr Institute and Natural History Museum of Denmark, University of

25



Copenhagen, Øster Voldgade 5-7, DK-1350 Copenhagen K, Denmark2 NASA Goddard Space Flight Center, Astrochemistry Laboratory, Mail Code 691, 8800 Greenbelt Road, Greenbelt,MD 20771, USA3 Department of Physics, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo, 113-0033, Japan

E-mail contact: johan.lindberg at nasa.gov

Context: The envelopes of molecular gas around embedded low-mass protostars show different chemistries, whichcan be used to trace their formation history and physical conditions. The excitation conditions of some molecularspecies can also be used to trace these physical conditions, making it possible to constrain e.g. sources of heating andexcitation.Aims: To study the range of influence of an intermediate-mass Herbig Be protostar, and to find what chemical andphysical impact feedback effects from the environment may have on embedded protostars.Methods: We follow up on an earlier line survey of the Class 0/I source R CrA IRS7B in the 0.8 mm window withan unbiased line survey of the same source in the 1.3 mm window using the Atacama Pathfinder Experiment (APEX)telescope. We also study the excitation of the key species H2CO, CH3OH, and c-C3H2 in a complete sample of the 18embedded protostars in the Corona Australis star-forming region. Radiative transfer models are employed to establishabundances of the molecular species.Results: We detect line emission from in total 20 molecular species (32 including isotopologues) in the two surveys.The most complex species detected are CH3OH, CH3CCH, CH3CHO, and CH3CN (the latter two are only tentativelydetected). CH3CN and several other complex organic molecules are significantly under-abundant in comparison withwhat is found towards “hot corino” protostars. The H2CO rotational temperatures of the sources in the region decreasewith the distance to the Herbig Be star R CrA, whereas the c-C3H2 temperatures remain constant across the star-forming region.Conclusions: The high H2CO temperatures observed towards objects close to R CrA suggest that this star has asphere of influence of several 10 000 AU in which it increases the temperature of the molecular gas to 30–50 K throughirradiation. The chemistry in the IRS7B envelope differs significantly from many other embedded protostars, whichcould be an effect of the external irradiation from R CrA.

Accepted by A&A

http://arxiv.org/pdf/1509.02514v1

Infall, outflow, and turbulence in massive star-forming cores in the G333 giant molecularcloud

N. Lo1, B. Wiles2, M.P. Redman2, M.R. Cunningham3, I. Bains4, P.A. Jones1,3, M.G. Burton3, and L.Bronfman1

1 Departamento de Astronomıa, Universidad de Chile, Camino El Observatorio 1515, Las Condes, Santiago, Casilla36-D, Chile2 Centre for Astronomy, School of Physics, National University of Ireland Galway, University Road, Galway, Ireland3 School of Physics, University of New South Wales, Sydney 2052, Australia4 Centre for Astrophysics and Supercomputing, Swinburne University of Technology, P.O. Box 218, Hawthorn, VIC3122, Australia

E-mail contact: nlo at das.uchile.cl

We present molecular line imaging observations of three massive molecular outflow sources, G333.6−0.2, G333.1−0.4,and G332.8−0.5, all of which also show evidence for infall, within the G333 giant molecular cloud (GMC). All threeare within a beam size (36′′) of IRAS sources, 1.2-mm dust clumps, various masing species and radio continuum-detected HII regions and hence are associated with high-mass star formation. We present the molecular line data andderive the physical properties of the outflows including the mass, kinematics, and energetics and discuss the inferredcharacteristics of their driving sources. Outflow masses are of 10 to 40 M⊙ in each lobe, with core masses of order103 M⊙. outflow size scales are a few tenth of a parsec, timescales are of several × 104 years, mass loss rates a few ×10−4 M⊙ yr−1. We also find the cores are turbulent and highly supersonic.

Accepted by MNRAS


26



Ambipolar diffusion in low-mass star formation. I. General comparison with the idealMHD case

J. Masson1, G. Chabrier1,2, P. Hennebelle3, N. Vaytet2, and B. Commercon2

1 School of Physics, University of Exeter, Exeter, EX4 4QL, UK2 Ecole Normale Superieure de Lyon, CRAL, UMR CNRS 5574, Universite de Lyon, 46 Allee d?Italie, 69364 LyonCedex 07, France3 Laboratoire de radioastronomie, UMR CNRS 8112, Ecole Normale Superieure et Observatoire de Paris, 24 rueLhomond, 75231 Paris Cedex 05, France

E-mail contact: jacques.masson at ens-lyon.fr

In this paper, we provide a more accurate description of the evolution of the magnetic flux redistribution duringprestellar core collapse by including resistive terms in the magnetohydrodynamics (MHD) equations. We focus moreparticularly on the impact of ambipolar diffusion. We use the adaptive mesh refinement code RAMSES to carry outsuch calculations. The resistivities required to calculate the ambipolar diffusion terms were computed using a reducedchemical network of charged, neutral and grain species. The inclusion of ambipolar diffusion leads to the formation of amagnetic diffusion barrier in the vicinity of the core, preventing accumulation of magnetic flux in and around the coreand amplification of the field above 0.1G. The mass and radius of the first Larson core remain similar between idealand non-ideal MHD models. This diffusion plateau has crucial consequences on magnetic braking processes, allowingthe formation of disk structures. Magnetically supported outflows launched in ideal MHD models are weakened whenusing non-ideal MHD. Contrary to ideal MHD misalignment between the initial rotation axis and the magnetic fielddirection does not significantly affect the results for a given µ, showing that the physical dissipation truly dominate overnumerical diffusion. We demonstrate severe limits of the ideal MHD formalism, which yield unphysical behaviours inthe long-term evolution of the system. This includes counter rotation inside the outflow, interchange instabilities, andflux redistribution triggered by numerical diffusion, none observed in non-ideal MHD. Disks with Keplerian velocityprofiles form in all our non-ideal MHD simulations, with final mass and size which depend on the initial magnetisation.This ranges from a few 0.01 M⊙ and 20–30 AU for the most magnetised case (µ = 2) to 0.2 M⊙ and 40–80 AU for alower magnetisation (µ = 5).

Accepted by A&A


The AU Mic Debris Disk: far-infrared and submillimeter resolved imaging

Brenda C. Matthews1,2, Grant Kennedy3, Bruce Sibthorpe4, Wayne Holland5,6, Mark Booth7, PaulKalas8,9, Meredith MacGregor10, David Wilner10, Bart Vandenbussche11, Goran Olofsson12, JorisBlommaert13,14, Alexis Brandeker12, W.R.F. Dent15, Bernard L. de Vries12,16, James Di Francesco1,2,Malcolm Fridlund17,18, James R. Graham8, Jane Greaves19, Ana M. Heras20, Michiel Hogerheijde18,R.J. Ivison21,5, Eric Pantin22, and Goran L. Pilbratt20

1 National Research Council of Canada Herzberg Astronomy & Astrophysics Programs, 5071 West Saanich Road,Victoria, BC, Canada, V9E 2E72 University of Victoria, 3800 Finnerty Road, Victoria, BC, V8P 5C2, Canada3 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK4 SRON Netherlands Institute for Space Research, Groningen, The Netherlands5 Institute for Astronomy, University of Edinburgh, Royal Observatory, Blackford Hill, Edinburgh EH9 3HJ, UK6 UK Astronomy Technology Centre, Science and Technology Facilities Council, Royal Observatory, Blackford Hill,Edinburgh, EH9 3HJ, UK7 Instituto de Astrofsica, Pontificia Universidad Catolica de Chile, Vicua Mackenna 4860, 7820436 Macul, Santiago,Chile8 Department of Astronomy, University of California, 601 Campbell Hall, Berkeley, CA, 94720, USA9 SETI Institute, Mountain View, CA 94043, USA10 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 USA11 Institute of Astronomy KU Leuven, Celestijnenlaan 200D, 3001 Leuven, Belgium12 Department of Astronomy, AlbaNova University Centre, Stockholm University, SE-106 91 Stockholm, Sweden13 Astronomy and Astrophysics Research Group, Department of Physics and Astrophysics, Vrije Universiteit Brussel,

27


Pleinlaan 2, 1050 Brussels, Belgium14 Flemish Institute for Technological Research (VITO), Boeretang 200, 2400 Mol, Belgium15 Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura 763-0355, Santiago, Chile16 Stockholm University Astrobiology Centre, SE-106 91 Stockholm, Sweden17 Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, 439 92,Onsala, Sweden18 Leiden Observatory, Leiden University, Postbus 9513, 2300 RA, Leiden, The Netherlands19 School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, Fife KY16 9SS, UK20 ESA, Scientific Support Office, Directorate of Science and Robotic Exploration, European Space Research andTechnology Centre (ESTEC/SRE-S), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands21 European Southern Observatory, Karl Schwarzschild Strasse 2, Garching, Germany22 Laboratoire AIM, CEA/DSM - CNRS - Universit Paris Diderot, IRFU/SAp, 91191 Gif sur Yvette, France

E-mail contact: brenda.matthews at nrc-cnrc.gc.ca

We present far-infrared and submillimeter maps from the Herschel Space Observatory and the James Clerk MaxwellTelescope of the debris disk host star AU Microscopii. Disk emission is detected at 70, 160, 250, 350, 450, 500 and850 µm. The disk is resolved at 70, 160 and 450 µm. In addition to the planetesimal belt, we detect thermal emissionfrom AU Mic’s halo for the first time. In contrast to the scattered light images, no asymmetries are evident in thedisk. The fractional luminosity of the disk is 3.9 × 10−4 and its mm-grain dust mass is 0.01 M⊕ (±20%). We create asimple spatial model that reconciles the disk SED as a blackbody of 53±2 K (a composite of 39 and 50 K components)and the presence of small (non-blackbody) grains which populate the extended halo. The best fit model is consistentwith the “birth ring” model explored in earlier works, i.e., an edge-on dust belt extending from 8.8–40 AU, but withan additional halo component with an r−1.5 surface density profile extending to the limits of sensitivity (140 AU). Weconfirm that AU Mic does not exert enough radiation force to blow out grains. For stellar mass loss rates of 10–100× solar, compact (zero porosity) grains can only be removed if they are very small, consistently with previous work,if the porosity is 0.9, then grains approaching 0.1 µm can be removed via corpuscular forces (i.e., the stellar wind).

Accepted by ApJ


A distance limited sample of massive star forming cores from the RMS survey

L.T. Maud1,2, S.L. Lumsden1, T.J.T. Moore3, J.C. Mottram2, J.S. Urquhart4, and A. Cicchini1,5

1 School of Physics and Astronomy, University of Leeds, Leeds, LS2 9JT, UK2 Leiden Observatory, Leiden University, PO Box 9513, 2300 RA Leiden, The Netherlands3 Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool, L5 3RF, UK4 Max-Planck-Institute fur Radioastronomie, Auf dem Hugel 69, D-53121 Bonn, Germany5 School of Physics and Astronomy, University of Nottingham, Nottingham, NG7 2RD, UK

E-mail contact: maud at strw.leidenuniv.nl

We analyse C18O (J=3–2) data from a sample of 99 infrared-bright massive young stellar objects (MYSOs) andcompact HII regions that were identified as potential molecular-outflow sources in the Red MSX source (RMS) survey.We extract a distance limited (D < 6 kpc) sample shown to be representative of star formation covering the transitionbetween the source types. At the spatial resolution probed, Larson-like relationships are found for these cores, thoughthe alternative explanation, that Larson’s relations arise where surface-density-limited samples are considered, is alsoconsistent with our data. There are no significant differences found between source properties for the MYSOs and HIIregions, suggesting that the core properties are established prior to the formation of massive stars, which subsequentlyhave little impact at the later evolutionary stages investigated. There is a strong correlation between dust-continuumand C18O-gas masses, supporting the interpretation that both trace the same material in these IR-bright sources. Aclear linear relationship is seen between the independently established core masses and luminosities. The position ofMYSOs and compact HII regions in the mass-luminosity plane is consistent with the luminosity expected a cluster ofprotostars when using a ∼40% star-formation efficiency and indicates that they are at a similar evolutionary stage,near the end of the accretion phase.

Accepted by MNRAS


28



CSO and CARMAObservations of L1157. I. A Deep Search for Hydroxylamine (NH2OH)

Brett A. McGuire1,2, P. Brandon Carroll2, Niklaus M. Dollhopf3,1, Nathan R. Crockett4, Joanna F.Corby3,1, Ryan A. Loomis5, Andrew Burkhardt2,1, Christopher Shingledecker3, Geoffrey A. Blake2,4,Anthony J. Remijan1

1 National Radio Astronomy Observatory, Charlottesville, VA 229032 Division of Chemistry and Chemical Engineering, California Institute of Technology, Pasadena, CA 911253 Department of Astronomy, University of Virginia, Charlottesville, VA 229034 Division of Geological and Planetary Sciences, California Institute of Technology, Pasadena, CA 911255 Department of Astronomy, Harvard University, Cambridge, MA 02138

E-mail contact: bmcguire at nrao.edu

A deep search for the potential glycine precursor hydroxylamine (NH2OH) using the Caltech Submillimeter Observa-tory (CSO) at λ=1.3 mm and the Combined Array for Research in Millimeter-wave Astronomy (CARMA) at λ=3 mmis presented toward the molecular outflow L1157, targeting the B1 and B2 shocked regions. We report non-detectionsof NH2OH in both sources. We a perform non-LTE analysis of CH3OH observed in our CSO spectra to derive kinetictemperatures and densities in the shocked regions. Using these parameters, we derive upper limit column densitiesof NH2OH of ≤1.4 × 1013 cm−2 and ≤1.5 × 1013 cm−2 toward the B1 and B2 shocks, respectively, and upper limitrelative abundances of NNH2OH/NH2

≤ 1.4× 10−8 and ≤1.5 × 10−8, respectively.

Accepted by ApJ


High resolution Brγ spectro-interferometry of the transitional Herbig Ae/Be star HD100546: a Keplerian gaseous disc inside the inner rim

I. Mendigutıa1, W.J. de Wit2, R.D. Oudmaijer1, J.R. Fairlamb1, A.D. Carciofi3, J.D. Ilee4 and R.G.Vieira3

1 School of Physics and Astronomy, University of Leeds, Woodhouse Lane, Leeds LS2 9JT, UK.2 European Southern Observatory, Casilla 19001, Santiago 19, Chile3 Instituto de Astronomia, Geofısica e Ciencias atmosfericas, Universidade de Sao Paulo (USP), Rua do Matao 1226,Cidade Universitaria, Sao Paulo, SP - 05508-900, Brazil4 SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS, UK

E-mail contact: I.Mendigutia at leeds.ac.uk

We present spatially and spectrally resolved Brγ emission around the planet-hosting, transitional Herbig Ae/Be starHD 100546. Aiming to gain insight into the physical origin of the line in possible relation to accretion processes,we carried out Brγ spectro-interferometry using AMBER/VLTI from three different baselines achieving spatial andspectral resolutions of 2 – 4 mas and 12000. The Brγ visibility is larger than that of the continuum for all baselines.Differential phases reveal a shift between the photocentre of the Brγ line –displaced ∼ 0.6 mas (0.06 au at 100 pc) NEfrom the star– and that of the K-band continuum emission –displaced ∼ 0.3 mas NE from the star. The photocentresof the redshifted and blueshifted components of the Brγ line are located NW and SE from the photocentre of thepeak line emission, respectively. Moreover, the photocentre of the fastest velocity bins within the spectral line tendsto be closer to that of the peak emission than the photocentre of the slowest velocity bins. Our results are consistentwith a Brγ emitting region inside the dust inner rim (<∼ 0.25 au) and extending very close to the central star, witha Keplerian, disc-like structure rotating counter-clockwise, and most probably flared (∼ 25◦). Even though the maincontribution to the Brγ line does not come from gas magnetically channelled on to the star, accretion on to HD100546 could be magnetospheric, implying a mass accretion rate of a few 10−7 M⊙ yr−1. This value indicates thatthe observed gas has to be replenished on time-scales of a few months to years, perhaps by planet-induced flows fromthe outer to the inner disc as has been reported for similar systems.

Accepted by MNRAS

[http://arxiv.org/pdf/1509.05411

29



Triggered fragmentation in self-gravitating discs: forming fragments at small radii

Farzana Meru1

1 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA, UK

E-mail contact: farzana.meru at ast.cam.ac.uk

We carry out three dimensional radiation hydrodynamical simulations of gravitationally unstable discs to explore themovement of mass in a disc following its initial fragmentation. We find that the radial velocity of the gas in someparts of the disc increases by up to a factor of ≈ 10 after the disc fragments, compared to before. While the movementof mass occurs in both the inward and outward directions, the inwards movement can cause the inner spirals of aself-gravitating disc to become sufficiently dense such that they can potentially fragment. This suggests that thedynamical behaviour of fragmented discs may cause subsequent fragmentation to occur at smaller radii than initiallyexpected, but only after an initial fragment has formed in the outer disc.

Accepted by Monthly Notices of the Royal Astronomical Society


Movies of Simulation 1 available at:

http://www.ast.cam.ac.uk/\%7Efmeru/Movies/massmovementsigma.mov and

http://www.ast.cam.ac.uk/\%7Efmeru/Movies/massmovementvR.mov

The JCMT Plane Survey: early results from the l = 30 degree field

T.J.T. Moore1, R. Plume2, M.A. Thompson3, H. Parsons4, J.S. Urquhart5, D.J. Eden1,6, J.T. Dempsey4,L.K. Morgan1, H.S. Thomas4, J. Buckle7,8, C.M. Brunt9, H. Butner10, D. Carretero8, A. Chrysostomou3,H.M. deVilliers3, M. Fich11, M.G. Hoare12, G. Manser3, J.C. Mottram13, C. Natario3, F. Olguin12, N.Peretto14, D. Polychroni15, R.O. Redman4, A.J. Rigby1, C. Salji8, L.J. Summers9, D. Berry4, M.J.Currie4, T. Jenness4,16, M. Pestalozzi17, A. Traficante18, P. Bastien19, J. diFrancesco20, C.J. Davis1,A. Evans21, P. Friberg4, G.A. Fuller18, A.G. Gibb22, S.J. Gibson23, T. Hill24, D. Johnstone4,20,25,G. Joncas26, S.N. Longmore1, S.L. Lumsden12, P.G. Martin27, Q. Nguy˜en Lu’o’ng27, J. E. Pineda18,C. Purcell28, J.S. Richer8, G.H. Schieven20, R. Shipman29, M. Spaans30, A.R. Taylor2, S. Viti31, B.eferling32, G.J. White33,34, M. Zhu35

1 Astrophysics Research Institute, Liverpool John Moores University, Ic2 Liverpool Science Park, 146 Brownlow HillLiverpool, L3 5RF, UK2 Department of Physics & Astronomy, University of Calgary, 2500 University Drive NW, Calgary, AB, T2N1N4,Canada3 Centre for Astrophysics Research, Science & Technology Research Institute, University of Hertfordshire, CollegeLane, Hatfield, Herts, AL10 9AB, UK4 Joint Astronomy Centre, 660 N. A’ohoku Place, University Park, Hilo, Hawaii 96720, USA5 Max-Planck-Institut fur Radioastronomie, Auf dem Hugel 69, 53121 Bonn, Germany6 Observatoire astronomique de Strasbourg, Universite de Strasbourg, CNRS, UMR 7550, France7 Astrophysics Group, Cavendish Laboratory, J J Thomson Avenue, Cambridge, CB3 0HE, UK8 Kavli Institute for Cosmology, Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB30HA, UK9 Astrophysics Group, School of Physics, University of Exeter, Stocker Road, Exeter EX4 4QL, UK10 Department of Physics and Astronomy, James Madison University, MSC 4502-901 Carrier Drive, Harrisonburg, VA22807, USA11 Department of Physics, University of Waterloo, Waterloo, Ontario N2L 3G1, Canada12 School of Physics and Astronomy, E C Stoner Building, University of Leeds, Leeds LS2 9JT, UK13 Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden, The Netherlands14 School of Physics and Astronomy, Cardiff University, Cardiff CF24 3AA, UK15 University of Athens, Department of Astrophysics, Astronomy and Mechanics, Faculty of Physics, Panepistimiopolis,15784 Zografos, Athens, Greece16 501 Space Sciences, Cornell University, Ithaca, NY 14853 USA17 Istituto di Astrofisica e Planetologia Spaziali (IAPS-INAF), via Fosso del Cavaliere 100, 00133, Roma, Italy

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http://www.ast.cam.ac.uk/%7Efmeru/Movies/massmovementsigma.mov

http://www.ast.cam.ac.uk/%7Efmeru/Movies/massmovementvR.mov

18 Jodrell Bank Centre for Astrophysics, School of Physics and Astronomy, The University of Manchester, OxfordRoad, Manchester M13 9PL, UK19 Centre de recherche en astrophysique du Quebec and Department de Physique, Universite de Montreal, Montreal,H3C 3J7, Canada20 NRC Herzberg Astronomy and Astrophysics, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada21 Astrophysics Group, Keele University, Keele, Staffordshire ST5 5BG, UK22 Department of Physics & Astronomy, University of British Columbia, 6224 Agricultural Road, Vancouver, BC V6T1Z1, Canada23 Department of Physics and Astronomy, Western Kentucky University, Bowling Green, KY 42101, USA24 Joint ALMA Observatory, 3107 Alonso de Cordova, Vitacura, Santiago, Chile25 Department of Physics and Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada26 Departement de physique, de genie physique et d’optique, Centre de Recherche en Astrophysique du Quebec,Universite Laval, QC G1K 7P4, Canada27 Canadian Institute for Theoretical Astrophysics, University of Toronto, 60 St. George Street, Toronto, ON M5S3H8, Canada28 Sydney Institute for Astronomy, School of Physics, The University of Sydney, NSW 2006, Australia29 SRON Netherlands Institute for Space Research, University of Groningen PO-Box 800, 9700 AV Groningen TheNetherlands30 Kapteyn Astronomical Institute, PO Box 800, NL-9700 AV Groningen, the Netherlands31 Department of Physics and Astronomy, University College London, WC1E 6BT London, UK32 Universitat Bamberg, Markusplatz 3, Bamberg, 96045 Germany33 Department of Physical Sciences, The Open University, Milton Keynes MK7 6AA, UK34 RALSpace, The Rutherford Appleton Laboratory, Chilton, Didcot OX11 0NL, UK35 National Astronomical Observatories, Chinese Academy of Science, 20A Datun Road, Chaoyang District, Beijing100012, China

E-mail contact: T.J.Moore at ljmu.ac.uk

We present early results from the JCMT Plane Survey (JPS), which has surveyed the northern inner Galactic planebetween longitudes l = 7◦ and l = 63◦ in the 850 µm continuum with SCUBA-2, as part of the James Clerk MaxwellTelescope Legacy Survey programme. Data from the l = 30◦ survey region, which contains the massive star-formingregions W43 and G29.96, are analysed after approximately 40% of the observations had been completed. The pixel-to-pixel noise is found to be 19 mJy beam−1, after a smooth over the beam area, and the projected equivalent noise levelsin the final survey are expected to be around 10 mJy beam−1. An initial extraction of compact sources was performedusing the FellWalker method resulting in the detection of 1029 sources above a 5σ surface-brightness threshold. Thecompleteness limits in these data are estimated to be around 0.2 Jy beam−1 (peak flux density) and 0.8 Jy (integratedflux density) and are therefore probably already dominated by source confusion in this relatively crowded sectionof the survey. The flux densities of extracted compact sources are consistent with those of matching detections inthe shallower ATLASGAL survey. We analyse the virial and evolutionary state of the detected clumps in the W43star-forming complex and find that they appear younger than the Galactic-plane average.

Accepted by MNRAS


The CH+ Abundance in Turbulent, Diffuse Molecular Clouds

Andrew T. Myers1, Christopher F. McKee2,3, and Pak Shing Li3

1 Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA, 94720, USA2 Department of Physics, University of California, Berkeley, Berkeley, CA 94720, USA3 Department of Astronomy, University of California, Berkeley, Berkeley, CA 94720, USA

E-mail contact: atmyers at lbl.gov

The intermittent dissipation of interstellar turbulence is an important energy source in the diffuse ISM. Though onaverage smaller than the heating rates due to cosmic rays and the photoelectric effect on dust grains, the turbulentcascade can channel large amounts of energy into a relatively small fraction of the gas that consequently undergoessignificant heating and chemical enrichment. In particular, this mechanism has been proposed as a solution to the

31


long-standing problem of the high abundance of CH+ along diffuse molecular sight lines, which steady-state, lowtemperature models under-produce by over an order of magnitude. While much work has been done on the structureand chemistry of these small-scale dissipation zones, comparatively little attention has been paid to relating thesezones to the properties of the large-scale turbulence. In this paper, we attempt to bridge this gap by estimatingthe temperature and CH+ column density along diffuse molecular sight-lines by post-processing 3-dimensional MHDturbulence simulations. Assuming reasonable values for the cloud density (30 cm−3), size (20 pc), and velocitydispersion (2.3 km s−1), we find that our computed abundances compare well with CH+ column density observations,as well as with observations of emission lines from rotationally excited H2 molecules.

Accepted by MNRAS


Chemical evolution of the HC3N and N2H+ molecules in dense cores of the Vela C giant

molecular cloud complex

Satoshi Ohashi1, Ken’ichi Tatematsu2,3, Kosuke Fujii1, Patricio Sanhueza2, Quang Nguyen Luong2,Minho Choi4, Tomoya Hirota2 and Norikazu Mizuno1,2

1 Department of Astronomy, School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 133-0033,Japan2 National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan3 Department of Astronomical Science, SOKENDAI (The Graduate University for Advanced Studies), 2-21-1 Osawa,Mitaka, Tokyo 181-85884 Korea Astronomy and Space Science Institute, Daedeokdaero 7 76, Yuseong, Daejeon 305-348, South Korea

E-mail contact: satoshi.ohashi at nao.ac.jp

We have observed the HC3N (J = 10 − 9) and N2H+ (J = 1 − 0) lines toward the Vela C molecular clouds with the

Mopra 22 m telescope to study chemical characteristics of dense cores. The intensity distributions of these moleculesare similar to each other at an angular resolution of 53′′, corresponding to 0.19 pc suggesting that these molecules tracethe same dense cores. We identified 25 local peaks in the velocity-integrated intensity maps of the HC3N and/or N2H

+

emission. Assuming LTE conditions, we calculated the column densities of these molecules and found a tendency thatN2H

+/HC3N abundance ratio seems to be low in starless regions while it seems to be high in star-forming regions,similar to the tendencies in the NH3/CCS, NH3/HC3N, and N2H

+/CCS abundance ratios found in previous studies ofdark clouds and the Orion A GMC. We suggest that carbon chain molecules, including HC3N, may trace chemicallyyoung molecular gas and N-bearing molecules, such as N2H

+, may trace later stages of chemical evolution in the VelaC molecular clouds. It may be possible that the N2H

+/HC3N abundance ratio of sim 1.4 divides the star-formingand starless peaks in the Vela C, although it is not as clear as those in NH3/CCS, NH3/HC3N, and N2H

+/CCS forthe Orion A GMC. This less clear separation may be caused by our lower spatial resolution or the misclassificationof star-forming and starless peaks due to the larger distance of the Vela C. It might be also possible that the HC3N(J = 10− 9) transition is not a good chemical evolution tracer compared with CCS (J = 4− 3 and 7− 6) transitions.

Accepted by PASJ

http://arxiv.org/pdf/1509.08642.pdf

Impact of the initial disk mass function on the disk fraction

Ryou Ohsawa1, Takashi Onaka2, Chikako Yasui2

1 Institute of Astronomy, University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015, Japan2 Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo113-0033, Japan

E-mail contact: ohsawa at astron.s.u-tokyo.ac.jp

The disk fraction, the percentage of stars with disks in a young cluster, is widely used to investigate the lifetime of theprotoplanetary disk, which can impose an important constraint on the planet formation mechanism. The relationshipbetween the decay timescale of the disk fraction and the mass dissipation timescale of an individual disk, however,remains unclear. Here we investigate the effect of the disk mass function (DMF) on the evolution of the disk fraction.

32



We show that the time variation in the disk fraction depends on the spread of the DMF and the detection threshold ofthe disk. In general, the disk fraction decreases more slowly than the disk mass if a typical initial DMF and a detectionthreshold are assumed. We find that, if the disk mass decreases exponentially, the mass dissipation timescale of thedisk can be as short as 1 Myr even when the disk fraction decreases with the time constant of ∼2.5 Myr. The decaytimescale of the disk fraction can be an useful parameter to investigate the disk lifetime, but the difference betweenthe mass dissipation of an individual disk and the decrease in the disk fraction should be properly appreciated toestimate the timescale of the disk mass dissipation.

Accepted by PASJ


Cosmic-ray acceleration in young protostars

Marco Padovani1,2, Patrick Hennebelle3, Alexandre Marcowith1 and Katia Ferriere4

1 Laboratoire Univers et Particules, Universite de Montpellier, France2 INAF–Osservatorio Astrofisico di Arcetri, Firenze, Italy3 CEA, IRFU, SAp, Centre de Saclay, Gif-Sur-Yvette, France4 IRAP, Universite de Toulouse, France

E-mail contact: Marco.Padovani at umontpellier.fr

The main signature of the interaction between cosmic rays and molecular clouds is the high ionisation degree. Thisdecreases towards the densest parts of a cloud, where star formation is expected, because of energy losses and magneticeffects. However recent observations hint to high levels of ionisation in protostellar systems, therefore leading toan apparent contradiction that could be explained by the presence of energetic particles accelerated within youngprotostars. Our modelling consists of a set of conditions that has to be satisfied in order to have an efficient particleacceleration through the diffusive shock acceleration mechanism. We find that jet shocks can be strong acceleratorsof protons which can be boosted up to relativistic energies. Another possibly efficient acceleration site is locatedat protostellar surfaces, where shocks caused by impacting material during the collapse phase are strong enough toaccelerate protons. Our results demonstrate the possibility of accelerating particles during the early phase of a proto-Solar-like system and can be used as an argument to support available observations. The existence of an internalsource of energetic particles can have a strong and unforeseen impact on the star and planet formation process as wellas on the formation of pre-biotic molecules.



Narrow Na and K Absorption Lines Toward T Tauri Stars - Tracing the Atomic Envelopeof Molecular Clouds

I. Pascucci1, S. Edwards2, M. Heyer3, E. Rigliaco4, L. Hillenbrand5, U. Gorti6, D. Hollenbach6 and M.N. Simon1

1 Lunar and Planetary Laboratory, The University of Arizona, Tucson, AZ 85721, USA2 Five College Astronomy Department, Smith College, Northampton, MA 01063, USA3 Department of Astronomy, University of Massachusetts, Amherst, MA 01003-9305, USA4 Institute for Astronomy, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich, Switzerland5 Department of Astronomy, California Institute of Technology, Pasadena, CA 91125, USA6 SETI Institute, Mountain View, CA 94043, USA

E-mail contact: pascucci at lpl.arizona.edu

We present a detailed analysis of narrow Na i and K i absorption resonance lines toward nearly 40 T Tauri stars inTaurus with the goal of clarifying their origin. The Na i 5889.95 A line is detected toward all but one source, while theweaker K i 7698.96 A line in about two thirds of the sample. The similarity in their peak centroids and the significantpositive correlation between their equivalent widths demonstrate that these transitions trace the same atomic gas. Theabsorption lines are present towards both disk and diskless young stellar objects, which excludes cold gas within thecircumstellar disk as the absorbing material. A comparison of Na i and CO detections and peak centroids demonstrates

33



that the atomic and molecular gas are not co-located, the atomic gas is more extended than the molecular gas. Thewidth of the atomic lines corroborates this finding and points to atomic gas about an order of magnitude warmerthan the molecular gas.The distribution of Na i radial velocities shows a clear spatial gradient along the length ofthe Taurus molecular cloud filaments. This suggests that absorption is associated with the Taurus molecular cloud.Assuming the gradient is due to cloud rotation, the rotation of the atomic gas is consistent with differential galacticrotation while the rotation of the molecular gas, although with the same rotation axis, is retrograde. Our analysisshows that narrow Na i and K i absorption resonance lines are useful tracers of the atomic envelope of molecularclouds. In line with recent findings from giant molecular clouds, our results demonstrate that the velocity fields of theatomic and molecular gas are misaligned. The angular momentum of a molecular cloud is not simply inherited fromthe rotating Galactic disk from which it formed but may be redistributed by cloud-cloud interactions.



The dust grain size – stellar luminosity trend in debris discs

Nicole Pawellek1 and Alexander V. Krivov1

1 Astrophysikalisches Institut und Universitatssternwarte, Friedrich-Schiller-Universitat, Schillergaßchen 2-3, 07745Jena, Germany

E-mail contact: nicole.pawellek at uni-jena.de

The cross section of material in debris discs is thought to be dominated by the smallest grains that can still stayin bound orbits despite the repelling action of stellar radiation pressure. Thus the minimum (and typical) grainsize smin is expected to be close to the radiation pressure blowout size sblow. Yet a recent analysis of a sample ofHerschel-resolved debris discs showed the ratio smin/sblow to systematically decrease with the stellar luminosity fromabout ten for solar-type stars to nearly unity in the discs around the most luminous A-type stars. Here we explorethis trend in more detail, checking how significant it is and seeking to find possible explanations. We show that thetrend is robust to variation of the composition and porosity of dust particles. For any assumed grain properties andstellar parameters, we suggest a recipe of how to estimate the “true” radius of a spatially unresolved debris disc, basedsolely on its spectral energy distribution. The results of our collisional simulations are qualitatively consistent withthe trend, although additional effects may also be at work. In particular, the lack of grains with small smin/sblowfor lower luminosity stars might be caused by the grain surface energy constraint that should limit the size of thesmallest collisional fragments. Also, a better agreement between the data and the collisional simulations is achievedwhen assuming debris discs of more luminous stars to have higher dynamical excitation than those of less luminousprimaries. This would imply that protoplanetary discs of more massive young stars are more efficient in forming bigplanetesimals or planets that act as stirrers in the debris discs at the subsequent evolutionary stage.

Accepted by MNRAS


Grain Growth in the Circumstellar Disks of the Young Stars CY Tau and DoAr 25

Laura M. Perez1,2, Claire J. Chandler1, Andrea Isella3, John M. Carpenter4, Sean M. Andrews5, NuriaCalvet6, Stuartt A. Corder7, Adam T. Deller8, Cornelis P. Dullemond9, Jane S. Greaves10, Robert J.Harris11, Thomas Henning12, Woojin Kwon13, Joseph Lazio14, Hendrik Linz12, Lee G. Mundy15, LucaRicci5, Anneila I. Sargent4, Shaye Storm15, Marco Tazzari16, Leonardo Testi16,17, David J. Wilner5

1 National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801, USA2 Jansky Fellow of the National Radio Astronomy Observatory3 Rice University, 6100 Main Street, Houston, TX 77005, USA4 California Institute of Technology, 1200 East California Blvd, Pasadena, CA 91125, USA5 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA6 University of Michigan, 830 Dennison Building, 500 Church Street, Ann Arbor, MI 48109, USA7 Joint ALMA Observatory, Av. Alonso de C?ordova 3107, Vitacura, Santiago, Chile8 The Netherlands Institute for Radio Astronomy (ASTRON), 7990-AA Dwingeloo, The Netherlands

34



9 Heidelberg University, Center for Astronomy, Albert Ueberle Str 2, Heidelberg, Germany10 University of St. Andrews, Physics and Astronomy, North Haugh, St Andrews KY16 9SS11 University of Illinois, 1002 West Green St., Urbana, IL 61801, USA12 Max-Planck-Institut fur Astronomie, Konigstuhl 17, 69117 Heidelberg, Germany13 Korea Astronomy and Space Science Institute, 776 Daedeok-daero, Yuseong-gu, Daejeon 34055, Korea14 Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr, Pasadena, CA 9110615 University of Maryland, College Park, MD 20742, USA16 European Southern Observatory, Karl Schwarzschild str. 2, 85748 Garching, Germany17 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy

E-mail contact: lperez at nrao.edu

We present new results from the Disks@EVLA program for two young stars: CY Tau and DoAr 25. We tracecontinuum emission arising from their circusmtellar disks from spatially resolved observations, down to tens of AUscales, at λ = 0.9, 2.8, 8.0, and 9.8 mm for DoAr25 and at λ = 1.3, 2.8, and 7.1 mm for CY Tau. Additionally,we constrain the amount of emission whose origin is different from thermal dust emission from 5 cm observations.Directly from interferometric data, we find that observations at 7 mm and 1 cm trace emission from a compactdisk while millimeter-wave observations trace an extended disk structure. From a physical disk model, where wecharacterize the disk structure of CY Tau and DoAr 25 at wavelengths shorter than 5 cm, we find that (1) dustcontinuum emission is optically thin at the observed wavelengths and over the spatial scales studied, (2) a constantvalue of the dust opacity is not warranted by our observations, and (3) a high-significance radial gradient of the dustopacity spectral index, β, is consistent with the observed dust emission in both disks, with low-β in the inner diskand high-β in the outer disk. Assuming that changes in dust properties arise solely due to changes in the maximumparticle size (amax), we constrain radial variations of amax in both disks, from cm-sized particles in the inner disk(R < 40 AU) to millimeter sizes in the outer disk (R > 80 AU). These observational constraints agree with theoreticalpredictions of the radial-drift barrier, however, fragmentation of dust grains could explain our amax(R) constraints ifthese disks have lower turbulence and/or if dust can survive high-velocity collisions.

Accepted by ApJ


Testing particle trapping in transition disks with ALMA

P. Pinilla1, N. van der Marel1, L. M. Perez2,3, E. F. van Dishoeck1,4, S. Andrews5, T. Birnstiel5, G.Herczeg6, K. M. Pontoppidan7 and T. van Kempen1

1 Leiden Observatory, Leiden University, P.O. Box 9513, 2300RA Leiden, The Netherlands2 National Radio Astronomy Observatory, P.O. Box O, Socorro NM 87801, USA3 Jansky Fellow4 Max-Planck-Institut fur Extraterrestrische Physik, Giessenbachstrasse 1, 85748, Garching, Germany5 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138, USA6 Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Haidian District, Beijing100871, China7 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA

E-mail contact: pinilla at strw.leidenuniv.nl

Some protoplanetary disks show evidence of inner dust cavities. Recent observations of gas and dust of these so-calledtransition disks have given major support to the hypothesis that the origin of such cavities is trapping in pressurebumps. We present new Atacama Large Millimeter/submillimeter Array (ALMA) continuum observations at 336 GHzof two transition disks, SR21 and HD 135344B. In combination with previous ALMA observations from Cycle 0 at689 GHz, we compare the visibility profiles at the two frequencies and calculate the spectral index (αmm). Theobservations of SR 21 show a clear shift in the visibility nulls, indicating radial variations of the inner edge of thecavity at the two wavelengths. Notable radial variations of the spectral index are also detected for SR 21 with valuesof αmm ∼ 3.8− 4.2 in the inner region (r<∼35 AU) and αmm ∼ 2.6− 3.0 outside. An axisymmetric ring (“ring model”)or a ring with the addition of an azimuthal Gaussian profile, for mimicking a vortex structure (“vortex model”), isassumed for fitting the disk morphology. For SR 21, the ring model better fits the emission at 336 GHz, conversely thevortex model better fits the 689 GHz emission. For HD 135344B, neither a significant shift in the null of the visibilities

35


nor radial variations of αmm are detected. Furthermore, for HD 135344B, the vortex model fits both frequenciesbetter than the ring model. However, the azimuthal extent of the vortex increases with wavelength, contrary to modelpredictions for particle trapping by anticyclonic vortices. For both disks, the azimuthal variations of αmm remainuncertain to confirm azimuthal trapping. The comparison of the current data with a generic model of dust evolutionthat includes planet-disk interaction suggests that particles in the outer disk of SR 21 have grown to millimetre sizesand have accumulated in a radial pressure bump, whereas with the current resolution there is not clear evidence ofradial trapping in HD 135344B, although it cannot be excluded either.

Accepted by A&A


Chemical Imaging of the CO Snow Line in the HD 163296 Disk

Chunhua Qi1, Karin I. Oberg1, Sean, M. Andrews1, David, J. Wilner1, Edwin A. Bergin2, A. MeredithHughes3, Michiel Hogherheijde4 and Paola D’Alessio5

1 Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138, USA2 University of Michigan, Ann Arbor, MI 48109, USA3 Wesleyan University, Middletown, CT 06459, USA4 Leiden University, 2300 RA Leiden, The Netherlands5 UNAM, 58089 Morelia, Michoacan, Mexico

E-mail contact: cqi at cfa.harvard.edu

The condensation fronts (snow lines) of H2O, CO and other abundant volatiles in the midplane of a protoplanetary diskaffect several aspects of planet formation. Locating the CO snow line, where the CO gas column density is expected todrop substantially, based solely on CO emission profiles is challenging. This has prompted an exploration of chemicalsignatures of CO freeze-out. We present ALMA Cycle 1 observations of the N2H

+ J = 3 − 2 and DCO+ J = 4 − 3emission lines toward the disk around the Herbig Ae star HD 163296 at ∼ 0.5′′ (60 AU) resolution, and evaluate theirutility as tracers of the CO snow line location. The N2H

+ emission is distributed in a ring with an inner radius at90 AU, corresponding to a midplane temperature of 25 K. This result is consistent with a new analysis of opticallythin C18O data, which implies a sharp drop in CO abundance at 90 AU. Thus N2H

+ appears to be a robust tracerof the midplane CO snow line. The DCO+ emission also has a ring morphology, but neither the inner nor the outerradius coincides with the CO snow line location of 90 AU, indicative of a complex relationship between DCO+ emissionand CO freeze-out in the disk midplane. Compared to TW Hya, CO freezes out at a higher temperature in the diskaround HD 163296 (25 vs. 17 K in the TW Hya disk), perhaps due to different ice compositions. This highlightsthe importance of actually measuring the CO snow line location, rather than assuming a constant CO freeze-outtemperature for all disks.

Accepted by ApJ


Kepler observations of A–F pre-main sequence stars in Upper Scorpius: Discovery ofsix new δ Scuti and one γ Doradus stars

V. Ripepi1, L. Balona2, G. Catanzaro3, M. Marconi1, F. Palla4, M. Giarrusso5

1 INAF-Osservatorio Astronomico di Capodimonte, Via Moiariello 16, I-80131, Napoli, Italy2 South African Astronomical Observatory, PO Box 9, Observatory 7935, Cape Town, South Africa3 INAF-Osservatorio Astrofisico di Catania, Via S.Sofia 78, I-95123, Catania, Italy4 Osservatorio Astrofisico di Arcetri, Firenze, Italy5 Universita degli studi di Catania, Via S.Sofia 78, I-95123 Catania, Italy

E-mail contact: ripepi at oacn.inaf.it

We present light curves and periodograms for 27 stars in the young Upper Scorpius association (age=11±1Myr)obtained with the Kepler spacecraft. This association is only the second stellar grouping to host several pulsating pre-main sequence (PMS) stars which have been observed from space. From an analysis of the periodograms, we identifysix δ Scuti variables and one γ Doradus star. These are most likely PMS stars or else very close to the zero-age main

36



sequence. Four of the δ Scuti variables were observed in short-cadence mode, which allows us to resolve the entirefrequency spectrum. For these four stars, we are able to infer some qualitative information concerning their ages.For the remaining two δ Scuti stars, only long-cadence data are available, which means that some of the frequenciesare likely to be aliases. One of the stars appears to be a rotational variable in a hierarchical triple system. This isa particularly important object, as it allows the possibility of an accurate mass determination when radial velocityobservations become available. We also report on new high-resolution echelle spectra obtained for some of the starsof our sample.

Accepted by MNRAS


A network of filaments detected by Herschel in the Serpens Core:A laboratory to test simulations of low-mass star formation

V. Roccatagliata1, J. E. Dale1,2, T. Ratzka3, L. Testi4,5,2, A. Burkert1,2, C. Koepferl6,7, A. Sicilia-Aguilar8,9, C. Eiroa9 and B. Gaczkowski1

1 Universitats-Sternwarte Munchen, Ludwig-Maximilians-Universitat, Scheinerstr. 1, 81679 Munchen, Germany2 Excellence Cluster ‘Universe’, Boltzmannstr. 2, 85748 Garching bei Munchen, Germany3 nstitute for Physics / IGAM, NAWI Graz, Karl-Franzens-Universitat, Universitatsplatz 5/II, 8010 Graz, Austria4 ESO, Karl-Schwarzschild-Strasse 2 D-85748 Garching bei Munchen, Germany5 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy6 Max Planck Institute for Astronomy, Konigstuhl 17, 69117 Heidelberg, Germany7 Max Planck International Research School for Astronomy and Cosmology, Heidelberg, Germany8 SUPA, School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews KY16 9SS, UK9 Departamento de Fısica Teorica, Facultad de Ciencias, Universidad Autonoma de Madrid, 28049 Cantoblanco,Madrid, Spain

E-mail contact: vrocca at usm.uni-muenchen.de

Context. Filaments represent a key structure during the early stages of the star formation process. Simulations showthat filamentary structures commonly formed before and during the formation of cores.Aims. The Serpens Core is an ideal laboratory for testing the state of the art of simulations of turbulent GiantMolecular Clouds.Methods. We used Herschel observations of the Serpens Core to compute temperature and column density maps ofthe region. We selected the early stages of a recent simulation of star-formation, before stellar feedback was initiated,with similar total mass and physical size as the Serpens Core. We also derived temperature and column density mapsfrom the simulations. The observed distribution of column densities of the filaments was analyzed, first including andthen masking the cores. The same analysis was performed on the simulations as well.Results. A radial network of filaments was detected in the Serpens Core. The analyzed simulation shows a strikingmorphological resemblance to the observed structures. The column density distribution of simulated filaments withoutcores shows only a log-normal distribution, while the observed filaments show a power-law tail. The power-law tailbecomes evident in the simulation if the focus is only the column density distribution of the cores. In contrast, theobserved cores show a flat distribution.Conclusions. Even though the simulated and observed filaments are subjectively similar–looking, we find that theybehave in very different ways. The simulated filaments are turbulence-dominated regions; the observed filaments areinstead self-gravitating structures that will probably fragment into cores.

Accepted by A&A

An ALMA Survey for Disks Orbiting Low-Mass Stars in the TW Hya Association

David R. Rodriguez1, Gerrit van der Plas1,2, Joel H. Kastner3, Adam C. Schneider4, Jacqueline K.Faherty5,6, Diego Mardones1, Subhanjoy Mohanty7, and David Principe2,8

1 Departamento de Astronomıa, Universidad de Chile, Casilla 36-D, Santiago, Chile2 Millennium Nucleus Protoplanetary Disks, Chile3 Center for Imaging Science, School of Physics & Astronomy, and Laboratory for Multiwavelength Astrophysics,

37


Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623, USA4 Department of Physics and Astronomy, University of Toledo, 2801 W. Bancroft St., Toledo, OH 43606, USA5 Department of Terrestrial Magnetism, Carnegie Institution of Washington, 5241 Broad Branch Road NW, Washing-ton, DC 20015, USA6 Hubble Fellow7 Imperial College London, 1010 Blackett Lab., Prince Consort Road, London SW7 2AZ, UK8 Nucleo de Astronomıa, Facultad de Ingenierıa, Universidad Diego Portales, Av. Ejercito 441, Santiago, Chile

E-mail contact: drodrigu at das.uchile.cl

We have carried out an ALMA survey of 15 confirmed or candidate low-mass (<0.2 M⊙) members of the TW HyaAssociation (TWA) with the goal of detecting molecular gas in the form of CO emission, as well as providing constraintson continuum emission due to cold dust. Our targets have spectral types of M4–L0 and hence represent the extremelow end of the TWA’s mass function. Our ALMA survey has yielded detections of 1.3mm continuum emission around4 systems (TWA 30B, 32, 33, & 34), suggesting the presence of cold dust grains. All continuum sources are unresolved.TWA 34 further shows 12CO(2–1) emission whose velocity structure is indicative of Keplerian rotation. Among thesample of known ∼7–10 Myr-old star/disk systems, TWA 34, which lies just ∼50 pc from Earth, is the lowest massstar thus far identified as harboring cold molecular gas in an orbiting disk.

Accepted by A&A


Terrestrial-type planet formation: Comparing different types of initial conditions

M.P. Ronco1, G.C. de Elıa1 and O.M. Guilera1

1 Facultad de Ciencias Astronmicas y Geofısicas, Universidad Nacional de La Plata and Instituto de Astrofsica de LaPlata, CCT La Plata-CONICET-UNLP, Paseo del Bosque S/N (1900), La Plata, Argentina

E-mail contact: mpronco at fcaglp.unlp.edu.ar

To study the terrestrial-type planet formation during the post oligarchic growth, the initial distributions of planetaryembryos and planetesimals used in N-body simulations play an important role. Most of these studies typically use adhoc initial distributions based on theoretical and numerical studies. We analyze the formation of planetary systemswithout gas giants around solar-type stars focusing on the sensitivity of the results to the particular initial distributionsof planetesimals and embryos. The formation of terrestrial planets in the habitable zone (HZ) and their final watercontents are topics of interest. We developed two different sets of N-body simulations from the same protoplanetarydisk. The first set assumes ad hoc initial distributions for embryos and planetesimals and the second set obtainsthese distributions from the results of a semi-analytical model which simulates the evolution of the gaseous phase ofthe disk. Both sets form planets in the HZ. Ad hoc initial conditions form planets in the HZ with masses from 0.66M⊕ to 2.27 M⊕. More realistic initial conditions obtained from a semi-analytical model, form planets with massesbetween 1.18 M⊕ and 2.21 M⊕. Both sets form planets in the HZ with water contents between 4.5% and 39.48% bymass. Those planets with the highest water contents respect to those with the lowest, present differences regardingthe sources of water supply. We suggest that the number of planets in the HZ is not sensitive to the particular initialdistribution of embryos and planetesimals and thus, the results are globally similar between both sets. However, themain differences are associated to the accretion history of the planets in the HZ. These discrepancies have a directimpact in the accretion of water-rich material and in the physical characteristics of the resulting planets.

Accepted by A&A


A possible link between the power spectrum of interstellar filaments and the origin ofthe prestellar core mass function

A. Roy1, Ph. Andre2, D. Arzoumanian1,2, N. Peretto3, P. Palmeirim1, V. Konyves1, N. Schneider1,4, M.Benedettini5, J. Di Francesco6,7, D. Elia5, T. Hill1,8, B. Ladjelate1, F. Louvet9, F. Motte1, S. Pezzuto5,E. Schisano5, Y. Shimajiri1, L. Spinoglio5, D. Ward-Thompson10, G. White11,12

1Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, IRFU / Service d’Astrophysique, C.E. Saclay, Orme

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des Merisiers, 91191 Gif-sur-Yvette2 Institut d’Astrophysique Spatiale, CNRS/Universite Paris-Sud 11, 91405 Orsay, France3 School of Physics & Astronomy, Cardiff University, Cardiff, CF29, 3AA, UK4 Universite de Bordeaux, LAB, CNRS/INSU, UMR 5804, BP 89, 33271, Floirac Cedex, France5 INAF-Istituto di Astrofisica e Planetologia Spaziali, via Fosso del Cavaliere 100, I-00133 Rome, Italy6 Department of Physics and Astronomy, University of Victoria, P.O. Box 355, STN CSC, Victoria, BC, V8W 3P6,Canada7 National Research Council Canada, 5071 West Saanich Road, Victoria, BC, V9E 2E7, Canada8 Joint ALMA Observatory, Alonso de Cordova 3107, Vitacura, Santiago, Chile9 Departamento de Astronomıa, Universidad de Chile, Santiago, Chile10 Jeremiah Horrocks Institute, University of Central Lancashire, Preston, Lancashire, PR1 2HE, UK11 Department of Physics and Astronomy, The Open University, Walton Hall Milton Keynes, MK7 6AA, UnitedKingdom12 RAL Space, STFC Rutherford Appleton Laboratory, Chilton Didcot, Oxfordshire OX11 0QX, United Kingdom

E-mail contact: Arabindo.roy at cea.fr, Philippe.andre at cea.fr

A complete understanding of the origin of the prestellar core mass function (CMF) is crucial. Two major features ofthe prestellar CMF are: 1) a broad peak below 1M⊙, presumably corresponding to a mean gravitational fragmentationscale, and 2) a characteristic power-law slope, very similar to the Salpeter slope of the stellar initial mass function(IMF) at the high-mass end. While recent Herschel observations have shown that the peak of the prestellar CMF isclose to the thermal Jeans mass in marginally supercritical filaments, the origin of the power-law tail of the CMF/IMFat the high-mass end is less clear. In 2001, Inutsuka proposed a theoretical scenario in which the origin of the power-lawtail can be understood as resulting from the growth of an initial spectrum of density perturbations seeded along thelong axis of star-forming filaments by interstellar turbulence. Here, we report the statistical properties of the line-massfluctuations of filaments in the Pipe, Taurus, and IC5146 molecular clouds observed with Herschel for a sample ofsubcritical or marginally supercritical filaments using a 1-D power spectrum analysis. The observed filament powerspectra were fitted by a power-law function (Ptrue(s) ∝ sα) after removing the effect of beam convolution at smallscales. A Gaussian-like distribution of power-spectrum slopes was found, centered at −1.6. The characteristic indexof the observed power spectra is close to that of the one-dimensional velocity power spectrum generated by subsonicKolomogorov turbulence (−1.67). Given the errors, the measured power-spectrum slope is also marginally consistentwith the power spectrum index of −2 expected for supersonic compressible turbulence. With such a power spectrumof initial line-mass fluctuations, Inutsuka’s model would yield a mass function of collapsed objects along filamentsapproaching dN/dM ∝ M−2.3±0.1 at the high-mass end (very close to the Salpeter power law) after a few free-falltimes. An empirical correlation, P 0.5(s0) ∝ 〈NH2

〉1.4±0.1, was also found between the amplitude of each filamentpower spectrum P (s0) and the mean column density along the filament 〈NH2

〉. Finally, the dispersion of line-massfluctuations along each filament σMline

was found to scale with the physical length L of the filament, roughly asσMline

∝ L0.7. Overall, our results are consistent with the suggestion that the bulk of the CMF/IMF results from thegravitational fragmentation of filaments.

Accepted by A&A


Velocity and magnetic fields within 1000 AU from a massive YSO

A. Sanna1, G. Surcis2, L. Moscadelli3, R. Cesaroni3, C. Goddi4, W.H.T. Vlemmings5 and A. Caratti oGaratti6

1 Max-Planck-Institut fuer Radioastronomie, Auf dem Huegel 69, 53121 Bonn, Germany2 JIVE, Joint Institute for VLBI in Europe, Postbus 2, 7990 AA Dwingeloo, The Netherlands3 INAF, Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy4 Department of Astrophysics/IMAPP, Radboud University Nijmegen, PO Box 9010, NL-6500 GL Nijmegen, TheNetherlands5 Department of Earth and Space Sciences, Chalmers University of Technology, Onsala Space Observatory, SE-439 92Onsala, Sweden6 Dublin Institute for Advanced Studies, School of Cosmic Physics, Astronomy & Astrophysics Section, 31 Fitzwilliam

39


Place, Dublin 2, Ireland

E-mail contact: asanna at mpifr-bonn.mpg.de

We want to study the velocity and magnetic field morphology in the vicinity (<1000 AU) of a massive young stellarobject (YSO), at very high spatial resolution (10-100 AU). We performed milli-arcsecond polarimetric observations ofthe strong CH3OH maser emission observed in the vicinity of an O-type YSO, in G023.01-00.41. We have combinedthis information with the velocity field of the CH3OH masing gas previously measured at the same angular resolution.We analyse the velocity and magnetic fields in the reference system defined by the direction of the molecular outflowand the equatorial plane of the hot molecular core at its base, as recently observed on sub-arcsecond scales. Weprovide a first detailed picture of the gas dynamics and magnetic field configuration within a radius of 2000 AU froma massive YSO. We have been able to reproduce the magnetic field lines for the outer regions (>600 AU) of themolecular envelope, where the magnetic field orientation shows a smooth change with the maser cloudlets position(0.2 degree/AU). Overall, the velocity field vectors well accommodate with the local, magnetic field direction, but stillshow an average misalignment of 30 degrees. We interpret this finding as the contribution of a turbulent velocity fieldof about 3.5 km/s, responsible for braking up the alignment between the velocity and magnetic field vectors. We doresolve different gas flows which develop both along the outflow axis and across the disk plane, with an average speedof 7 km/s. In the direction of the outflow axis, we establish a collimation of the gas flow, at a distance of about 1000AU from the disk plane. In the disk region, gas appears to stream outward along the disk plane for radii greater than500-600 AU, and inward for shorter radii.



Young Stellar Objects in the Massive Star Forming Region: W49

G. Saral1,2, J.L. Hora1, S.E. Willis1, X.P. Koenig3, R.A. Gutermuth4, A.T. Saygac5

1 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge 02138, MA2 Istanbul University, Graduate School of Science and Engineering, Bozdogan Kemeri Cad. 8, Vezneciler-Istanbul-Turkey3 Yale University, Department of Astronomy, 208101, New Haven, 06520-8101, CT4 University of Massachusetts, Department of Astronomy, Amherst, 01003, MA5 Istanbul University, Faculty of Science, Astronomy and Space Sciences Department, Istanbul-Turkey

E-mail contact: saralgozde at gmail.com

We present the initial results of our investigation of the star-forming complex W49, one of the youngest and mostluminous massive star forming regions in our Galaxy. We used Spitzer/Infrared Array Camera (IRAC) data toinvestigate massive star formation with the primary objective to locate a representative set of protostars and theclusters of young stars that are forming around them. We present our source catalog with the mosaics from the IRACdata. In this study we used a combination of IRAC, MIPS, Two Micron All Sky Survey (2MASS) and UKIRT DeepInfrared Sky Survey (UKIDSS) data to identify and classify the Young Stellar Objects (YSOs). We identified 232Class 0/I YSOs, 907 Class II YSOs, and 74 transition disk candidate objects using color-color and color-magnitudediagrams. In addition, to understand the evolution of star formation in W49 we analysed the distribution of YSOs inthe region to identify clusters using a minimal spanning tree method. The fraction of YSOs that belong to clusterswith >7 members is found to be 52% for a cut-off distance of 96′′ and the ratio of Class II/I objects is 2.1. Wecompared the W49 region to the G305 and G333 star forming regions and concluded that the W49 has the richestpopulation with 7 subclusters of YSOs.

Accepted by ApJ


X-ray to NIR emission from AA Tauri during the dim state – Occultation of the innerdisk and gas-to-dust ratio of the absorber

P.C. Schneider1,2, K. France3,7, H.M. Gunther4, G.J. Herczeg5, J. Robrade2, J. Bouvier6, M. McJunkin3,and J.H.M.M. Schmitt2

40



1 European Space Research and Technology Centre (ESA/ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Nether-lands2 Hamburger Sternwarte, Gojenbergsweg 112, Hamburg, 21029 Germany3 Center for Astrophysics and Space Astronomy, University of Colorado, 389 UCB, Boulder, CO 80309, USA4 Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02139, USA5 The Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Hai Dian Qu, Beijing100871, China6 Univ. Grenoble Alpes, IPAG, F-38000 Grenoble, France CNRS, IPAG, F-38000 Grenoble, France7 Laboratory for Atmospheric and Space Physics, University of Colorado, 392 UCB, Boulder, CO 80309

E-mail contact: christian.schneider at esa.int

AA Tau is a well-studied, nearby classical T Tauri star, which is viewed almost edge-on. A warp in its inner diskperiodically eclipses the central star, causing a clear modulation of its optical light curve. The system underwent amajor dimming event beginning in 2011 caused by an extra absorber, which is most likely associated with additionaldisk material in the line of sight toward the central source. We present new XMM-Newton X-ray, Hubble SpaceTelescope FUV, and ground based optical and near-infrared data of the system obtained in 2013 during the long-lasting dim phase. The line width decrease of the fluorescent H2 disk emission shows that the extra absorber is locatedat r > 1 AU. Comparison of X-ray absorption (NH) with dust extinction (AV ), as derived from measurements obtainedone inner disk orbit (eight days) after the X-ray measurement, indicates that the gas-to-dust ratio as probed by theNH to AV ratio of the extra absorber is compatible with the ISM ratio. Combining both results suggests that theextra absorber, i.e., material at r > 1 AU, has no significant gas excess in contrast to the elevated gas-to-dust ratiopreviously derived for material in the inner region (<∼0.1 AU).

Accepted by A&A


CSI 2264: Accretion process in classical T Tauri stars in the young cluster NGC 2264

A. P. Sousa1, S. H. P. Alencar1, J. Bouvier2,3, J. Stauffer4, L. Venuti2,3, L. Hillenbrand5, A.M. Cody6,P. S. Teixeira7, M. M. Guimares8, P. T. McGinnis1, L. Rebull4, E. Flaccomio9, G. Frsz10 and J. F.Gameiro11

1 Departmento de Fısica-Icex-UFMG, Antonio Carlos, 6627, 31270-90. Belo Horizonte, MG, Brazil2 Univ. Grenoble Alpes, IPAG, F-38000 Grenoble, France3 CNRS, IPAG, F-38000 Grenoble, France4 Spitzer Science Center, California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125,USA5 Astronomy Department, California Institute of Technology, Pasadena, CA 91125, USA6 NASA Ames Research Center, Kepler Science Office, Mountain View, CA 94035, USA7 Universitt Wien, Institut fr Astrophysik, Trkenschanzstrasse 17, 1180 Vienna, Austria8 Departmento de Fısica, Universidade Federal de Sergipe, Aracaju, SE, Brazil9 INAFOsservatorio Astronomico di Palermo, Piazza del Parlamento 1, I-90134 Palermo, Italy10 MIT Kavli Institute for Astrophysics and Space Research, 77 Mass Ave 37-582f, Cambridge, MA 02139, USA11 Instituto de Astrofsica e Cincias Espaciais and Faculdade de Cincias Universidade do Porto, CAUP, Rua da Estrelas,PT4150-762 Porto, Portugal

E-mail contact: alana at fisica.ufmg.br

NGC 2264 is a young stellar cluster (∼ 3 Myr) with hundreds of low-mass accreting stars that allow a detailed analysisof the accretion process taking place in the pre-main sequence. Our goal is to relate the photometric and spectroscopicvariability of classical T Tauri stars to the physical processes acting in the stellar and circumstellar environment, withina few stellar radii from the star. NGC 2264 was the target of a multiwavelength observational campaign with CoRoT,MOST, Spitzer, and Chandra satellites and photometric and spectroscopic observations from the ground. We classifiedthe CoRoT light curves of accreting systems according to their morphology and compared our classification to severalaccretion diagnostics and disk parameters. The morphology of the CoRoT light curve reflects the evolution of theaccretion process and of the inner disk region. Accretion burst stars present high mass-accretion rates and opticallythick inner disks. AA Tau-like systems, whose light curves are dominated by circumstellar dust obscuration, show

41


intermediate mass-accretion rates and are located in the transition of thick to anemic disks. Classical T Tauri starswith spot-like light curves correspond mostly to systems with a low mass-accretion rate and low mid-IR excess. About30% of the classical T Tauri stars observed in the 2008 and 2011 CoRoT runs changed their light-curve morphology.Transitions from AA Tau-like and spot-like to aperiodic light curves and vice versa were common. The analysis ofthe Hα emission line variability of 58 accreting stars showed that 8 presented a periodicity that in a few cases wascoincident with the photometric period. The blue and red wings of the Hα line profiles often do not correlate witheach other, indicating that they are strongly influenced by different physical processes. Classical T Tauri stars have adynamic stellar and circumstellar environment that can be explained by magnetospheric accretion and outflow models,including variations from stable to unstable accretion regimes on timescales of a few years.

Accepted by A&A


The Gaia-ESO Survey: chemical signatures of rocky accretion in a young solar-type star

L. Spina1, F. Palla2, S. Randich2, G. Sacco2, R. Jeffires3, L. Magrini2, E. Franciosini2, M.R. Meyer4,G. Tautvaisiene5, G. Gilmore6, E. J. Alfaro7, C. Allende Prieto8,9, T. Bensby10, A. Bragaglia11, E.Flaccomio12, S. E. Koposov6,13, A. C. Lanzafame14, M. T. Costado7, A. Hourihane6, C. Lardo15, J.Lewis6, L. Monaco16, L. Morbidelli2, S. G. Sousa17, C. C. Worley6 and S. Zaggia18

1 Departamento de Astronomia do IAG/USP, Universidade de So Paulo, Rua do Mtao 1226, So Paulo, 05509-900 SP,Brasil2 INAF - Osservatorio Astrofisico di Arcetri, Largo E. Fermi, 5, 50125, Firenze, Italy3 Astrophysics Group, Research Institute for the Environment, Physical Sciences and Applied Mathematics, KeeleUniversity, Keele, Staffordshire, ST5 5BG, United Kingdom4 Institute for Astronomy, ETH Zurich, Wolfgang-Pauli Strasse 27, 8093 Zurich, Switzerland5 Institute of Theoretical Physics and Astronomy, Vilnius University, A. Gostauto 12, 01108, Vilnius, Lithuania6 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, United Kingdom7 Instituto de Astrofsica de Andalucia-CSIC, Apdo. 3004, 18080, Granada, Spain8 Instituto de Astrofsica de Canarias, E-38205 La Laguna, Tenerife, Spain9 Universidad de La Laguna, Dept. Astrofisica, E-38206 La Laguna, Tenerife, Spain10 Lund Observatory, Department of Astronomy and Theoretical Physics, Box 43, SE-221 00 Lund, Sweden11 INAF - Osservatorio Astronomico di Bologna, via Ranzani 1, 40127, Bologna, Italy12 INAF - Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134, Palermo, Italy13 Moscow MV Lomonosov State University, Sternberg Astronomical Institute, Moscow 119992, Russia14 Dipartimento di Fisica e Astronomia, Sezione Astrofisica, Universita di Catania, via S. Sofia 78, 95123, Catania,Italy15 Astrophysics Research Institute, Liverpool John Moores University, 146 Brownlow Hill, Liverpool L3 5RF, UnitedKingdom16 Departamento de Ciencias Fisicas, Universidad Andres Bello, Re- publica 220, Santiago, Chile17 Instituto de Astrofsica e Ciencias do Espaco, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto,Portugal18 INAF - Padova Observatory, Vicolo dell Osservatorio 5, 35122 Padova, Italy

E-mail contact: lspina at usp.br

It is well known that newly formed planetary systems undergo processes of orbital reconfiguration and planetarymigration. As a result, planets or protoplanetary objects may accrete onto the central star, being fused and mixedinto its external layers. If the accreted mass is sufficiently high and the star has a sufficiently thin convective envelope,such events may result in a modification of the chemical composition of the stellar photosphere in an observable way,enhancing it with elements that were abundant in the accreted mass. The recent Gaia-ESO Survey observations ofthe 10-20 Myr old Gamma Velorum cluster have enabled identifying a star that is significantly enriched in iron withrespect to other cluster members. In this Letter we further investigate the abundance pattern of this star, showingthat its abundance anomaly is not limited to iron, but is also present in the refractory elements, whose overabundancesare correlated with the condensation temperature. This finding strongly supports the hypothesis of a recent accretionof rocky material.

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Accepted by Astronomy and Astrophysics


Searching for Trans Ethyl Methyl Ether in Orion KL

B. Tercero1, J. Cernicharo1, A. Lopez1,2, N. Brouillet3, L. Kolesnikova4, R.A. Motiyenko5, L. Margules5,J.L. Alonso4, and J.-C. Guillemin6

1 Grupo de Astrofısica Molecular. Instituto de CC. de Materiales de Madrid (ICMM-CSIC). Sor Juana Ines de laCruz, 3, Cantoblanco, 28049 Madrid, Spain2 Dpto. de Astrofısica, CAB. INTA-CSIC. Crta Torrejon-Ajalvir, km. 4. 28850 Torrejon de Ardoz. Madrid. Spain3 Univ. Bordeaux, LAB, UMR 5804, F-33270 Floirac, France; CNRS, LAB, UMR 5804, F-33270 Floirac, France4 Grupo de Espectroscopıa Molecular (GEM), Edificio Quifima, Area de Quımica-Fısica, Laboratorios de Espectro-scopıa y Bioespectroscopıa, Parque Cientfico UVa, Unidad Asociada CSIC, Universidad de Valladolid, 47011 Valladolid,Spain5 Laboratoire de Physique des Lasers, Atomes, et Molecules, UMR CNRS 8523, Universit de Lille I, F-59655 Villeneuved’Ascq Cedex, France6 Institut des Sciences Chimiques de Rennes, Ecole Nationale Superieure de Chimie de Rennes, CNRS, UMR 6226,11 Allee de Beaulieu, CS 50837, 35708 Rennes Cedex 7, France

E-mail contact: b.tercero at icmm.csic.es

We report on the tentative detection of trans Ethyl Methyl Ether (tEME), t-CH3CH2OCH3, through the identificationof a large number of rotational lines from each one of the spin states of the molecule towards Orion KL. We also searchfor gauche-trans-n-propanol, Gt-n-CH3CH2CH2OH, an isomer of tEME in the same source. We have identified linesof both species in the IRAM 30m line survey and in the ALMA Science Verification data. We have obtained ALMAmaps to establish the spatial distribution of these species. Whereas tEME mainly arises from the compact ridgecomponent of Orion, Gt-n-propanol appears at the emission peak of ethanol (south hot core). The derived columndensities of these species at the location of their emission peaks are ≤(4.0±0.8)×1015 cm−2 and ≤(1.0±0.2)×1015

cm−2 for tEME and Gt-n-propanol, respectively. The rotational temperature is ∼100K for both molecules. We alsoprovide maps of CH3OCOH, CH3CH2OCOH, CH3OCH3, CH3OH, and CH3CH2OH to compare the distribution ofthese organic saturated O-bearing species containing methyl and ethyl groups in this region. Abundance ratios ofrelated species and upper limits to the abundances of non-detected ethers are provided. We derive an abundance ratioN(CH3OCH3)/N(tEME)≥150 in the compact ridge of Orion.



A circumbinary disc model for the variability of the eclipsing binary CoRoT 223992193

Caroline Terquem1,2, Paul Magnus Sørensen–Clark3,4 and Jerome Bouvier3,5

1 Physics Department, University of Oxford, Keble Road, Oxford OX1 3RH, UK2 Institut d’Astrophysique de Paris, UPMC Univ Paris 06, CNRS, UMR7095, 98 bis bd Arago, F–75014, Paris, France3 Universite Grenoble Alpes, IPAG, F–38000 Grenoble, France4 Institute of Theoretical Astrophysics, University of Oslo, Oslo 0315, Norway5 CNRS, IPAG, F–38000 Grenoble, France

E-mail contact: caroline.terquem at physics.ox.ac.uk

We calculate the flux received from a binary system obscured by a circumbinary disc. The disc is modelled usingtwo dimensional hydrodynamical simulations, and the vertical structure is derived by assuming it is isothermal. Thegravitational torque from the binary creates a cavity in the disc’s inner parts. If the line of sight along which thesystem is observed has a high inclination I, it intersects the disc and some absorption is produced. As the systemis not axisymmetric, the resulting light curve displays variability. We calculate the absorption and produce lightcurves for different values of the dust disc aspect ratio H/r and mass of dust in the cavity Mdust. This model isapplied to the high inclination (I = 85◦) eclipsing binary CoRoT 223992193, which shows 5–10% residual photometricvariability after the eclipses and a spot model are subtracted. We find that such variations for I ∼ 85◦ can be obtained

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for H/r = 10−3 and Mdust ≥ 10−12 M⊙. For higher H/r, Mdust would have to be close to this lower value and Isomewhat less than 85◦. Our results show that such variability in a system where the stars are at least 90% visible atall phases can be obtained only if absorption is produced by dust located inside the cavity. If absorption is dominatedby the parts of the disc located close to or beyond the edge of the cavity, the stars are significantly obscured.

Accepted by MNRAS


Hunting for planets in the HL Tau disk

L. Testi1,2,3, A. Skemer4,5, Th. Henning6, V. Bailey4, D. Defrere4, Ph. Hinz4, J. Leisenring4, A. Vaz4,S. Esposito2, A. Fontana7, A. Marconi8, M. Skrutskie9 and C. Veillet10

1 ESO, Karl Schwarzschild str. 2, D-85748 Garching bei Muenchen, Germany2 INAF-Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, I-50125 Firenze, Italy3 Excellence Cluster ‘Universe’, Boltzmann str. 2, D-85748 Garching bei Muenchen, Germany4 Steward Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA5 University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA 95064, USA6 Max Planck Institute for Astronomie, Konigstuhl 17, D-69117 Heidelberg, Germany7 INAF-Osservatorio Astronomico di Roma, Monte Porzio, Italy8 Universita degli Studi di Firenze, Dipartimento di Fisica e Astronomia, Firenze, Italy9 University of Virginia, 530 McCormick Road, Charlottesville, VA 22904, USA10 LBT Observatory, University of Arizona, 933 N. Cherry Ave., Tucson, AZ 85721, USA

E-mail contact: ltesti at eso.org

Recent ALMA images of HL Tau show gaps in the dusty disk that may be caused by planetary bodies. Given theyoung age of this system, if confirmed, this finding would imply very short timescales for planet formation, probably ina gravitationally unstable disk. To test this scenario, we searched for young planets by means of direct imaging in theL′-band using the Large Binocular Telescope Interferometer mid-infrared camera. At the location of two prominentdips in the dust distribution at ∼70 AU (∼0.′′5) from the central star we reach a contrast level of ∼ 7.5 mag. Wedid not detect any point source at the location of the rings. Using evolutionary models we derive upper limits of∼10-15 MJup at ≤ 0.5-1 Ma for the possible planets. With these sensitivity limits we should have been able to detectcompanions sufficiently massive to open full gaps in the disk. The structures detected at mm-wavelengths could begaps in the distributions of large grains on the disk midplane, caused by planets not massive enough to fully opengaps. Future ALMA observations of the molecular gas density profile and kinematics as well as higher contrast infraredobservations may be able to provide a definitive answer.

Accepted by The Astrophysical Journal Letters


Turbulent mixing layers in supersonic protostellar outflows, with application to DGTauri

Marc C White1, Geoffrey V Bicknell1, Ralph Sutherland1, Raquel Salmeron1 and Peter J McGregor1

1 Research School of Astronomy & Astrophysics, The Australian National University, Mount Stromlo Observatory,Cotter Rd, Weston Creek, ACT, 2611, Australia

E-mail contact: marc.white at anu.edu.au

Turbulent entrainment processes may play an important role in the outflows from young stellar objects at all stagesof their evolution. In particular, lateral entrainment of ambient material by high-velocity, well-collimated protostellarjets may be the cause of the multiple emission-line velocity components observed in the microjet-scale outflows drivenby classical T Tauri stars. Intermediate-velocity outflow components may be emitted by a turbulent, shock-excitedmixing layer along the boundaries of the jet. We present a formalism for describing such a mixing layer based onReynolds decomposition of quantities measuring fundamental properties of the gas. In this model, the molecular windfrom large disc radii provides a continual supply of material for entrainment. We calculate the total stress profilein the mixing layer, which allows us to estimate the dissipation of turbulent energy, and hence the luminosity of the

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layer. We utilize mappings IV shock models to determine the fraction of total emission that occurs in [Fe ii] 1.644µm line emission in order to facilitate comparison to previous observations of the young stellar object DG Tauri. Ourmodel accurately estimates the luminosity and changes in mass outflow rate of the intermediate-velocity componentof the DG Tau approaching outflow. Therefore, we propose that this component represents a turbulent mixing layersurrounding the well-collimated jet in this object. Finally, we compare and contrast our model to previous work inthe field.

Accepted by MNRAS


No Keplerian Disk >10 AU around the Protostar B335: Magnetic Braking or YoungAge?

Hsi-Wei Yen1, Shigehisa Takakuwa1, Patrick M. Koch1, Yusuke Aso2, Shin Koyamatsu2,3, RubenKrasnopolsky1 and Nagayoshi Ohashi1,3

1 Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan2 Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo113-0033, Japan3 Subaru Telescope, National Astronomical Observatory of Japan, 650 North A’ohoku Place, Hilo, HI 96720, USA

E-mail contact: hwyen at asiaa.sinica.edu.tw

We have conducted ALMA cycle 2 observations in the 1.3 mm continuum and in the C18O (2–1) and SO (56–45) linesat a resolution of ∼0.′′3 toward the Class 0 protostar B335. The 1.3 mm continuum, C18O, and SO emission all showcentral compact components with sizes of ∼40–180 AU within more extended components. The C18O componentshows signs of infalling and rotational motion. By fitting simple kinematic models to the C18O data, the protostellarmass is estimated to be 0.05 M⊙. The specific angular momentum, on a 100 AU scale, is (4.3±0.5) × 10−5 km s−1

pc. A similar specific angular momentum, (3–5) × 10−5 km s−1 pc, is measured on a 10 AU scale from the velocitygradient observed in the central SO component, and there is no clear sign of an infalling motion in the SO emission.By comparing the infalling and rotational motion, our ALMA results suggest that the observed rotational motion hasnot yet reached Keplerian velocity neither on a 100 AU nor even on a 10 AU scale. Consequently, the radius of theKeplerian disk in B335 (if present) is expected to be 1–3 AU. The expected disk radius in B335 is one to two ordersof magnitude smaller than those of observed Keplerian disks around other Class 0 protostars. Based on the observedinfalling and rotational motion from 0.1 pc to inner 100 AU scales, there are two possible scenarios to explain thepresence of such a small Keplerian disk in B335: magnetic braking and young age. If our finding is the consequenceof magnetic braking, ∼50% of the angular momentum of the infalling material within a 1000 AU scale might havebeen removed, and the magnetic field strength on a 1000 AU scale is estimated to be ∼200 µG. If it is young age, theinfalling radius in B335 is estimated to be ∼2700 AU, corresponding to a collapsing time scale of ∼5 × 104 yr.

Accepted by ApJ


Origin and kinematics of the eruptive flow from XZ Tau revealed by ALMA

Luis A. Zapata1, Roberto Galvan-Madrid1, Carlos Carrasco-Gonzalez1, Salvador Curiel2, Aina Palau1,Luis F. Rodrıguez1, Stan E. Kurtz1, Daniel Tafoya1, and Laurent Loinard1

1 Instituto de Radioastronomıa y Astrofısica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacan, Mexico2 Instituto de Astronomıa, Universidad Nacional Autonoma de Mexico, Ap. 70-264, 04510 DF, Mexico

E-mail contact: [email protected]

We present high angular resolution (∼0.94′′) 12CO(1-0) Atacama Large Millimeter/Submillimeter Array (ALMA)observations obtained during the 2014 long baseline campaign from the eruptive bipolar flow from the multiple XZTau stellar system discovered by the Hubble Space Telescope (HST). These observations reveal, for the first time, thekinematics of the molecular flow. The kinematics of the different ejections close to XZ Tau reveal a rotating andexpanding structure with a southeast-northwest velocity gradient. The youngest eruptive bubbles unveiled in theoptical HST images are inside of this molecular expanding structure. Additionally, we report a very compact and

45



collimated bipolar outflow emanating from XZ Tau A, which indicates that the eruptive outflow is indeed originatingfrom this object. The mass (3 × 10−7 M⊙) and energetics (Ekin = 3 × 1037 ergs) for the collimated outflow arecomparable with those found in molecular outflows associated with young brown dwarfs.

Accepted by ApJ Letters


On the IMF in a Triggered Star Formation Context

Tingtao Zhou1,2, Chelsea X. Huang1,3, D.N.C. Lin1,4,5, Matthias Gritschneder4,6, and Herbert Lau7

1 Kavli Institute for Astronomy & Astrophysics and School of Physics, Peking University, Beijing China2 Department of Physics, MIT, USA3 Department of Astrophysical Sciences, Princeton University, USA4 UCO/Lick Observatory, University of California, USA5 Institute for Advanced Studies, Tsinghua University, Beijing, China6 University Observatory Munich, Germany7 Argelander Institute, University of Bonn, Germany

E-mail contact: edmondztt at gmail.com

The origin of the stellar initial mass function (IMF) is a fundamental issue in the theory of star formation. It isgenerally fit with a composite power law. Some clues on the progenitors can be found in dense starless cores thathave a core mass function (CMF) with a similar shape. In the low-mass end, these mass functions increase with mass,albeit the sample may be somewhat incomplete; in the high-mass end, the mass functions decrease with mass. Thereis an offset in the turn-over mass between the two mass distributions. The stellar mass for the IMF peak is lower thanthe corresponding core mass for the CMF peak in the Pipe Nebula by about a factor of three. Smaller offsets arefound between the IMF and the CMFs in other nebulae. We suggest that the offset is likely induced during a starburstepisode of global star formation which is triggered by the formation of a few O/B stars in the multi-phase media,which naturally emerged through the onset of thermal instability in the cloud-core formation process. We considerthe scenario that the ignition of a few massive stars photoionizes the warm medium between the cores, increases theexternal pressure, reduces their Bonnor-Ebert mass, and triggers the collapse of some previously stable cores. Wequantitatively reproduce the IMF in the low-mass end with the assumption of additional rotational fragmentation.

Accepted by ApJ


The Structure of Spiral Shocks Excited by Planetary-mass Companions

Zhaohuan Zhu1, Ruobing Dong2,3, James M. Stone1 and Roman R. Rafikov1

1 Department of Astrophysical Sciences, 4 Ivy Lane, Peyton Hall, Princeton University, Princeton, NJ 08544, USA2 Lawrence Berkeley National Lab, Berkeley, CA 94720, USA3 Department of Astronomy, University of California at Berkeley, Berkeley, CA 94720, USA

E-mail contact: zhzhu at astro.princeton.edu

Direct imaging observations have revealed spiral structures in protoplanetary disks. Previous studies have suggestedthat planet-induced spiral arms cannot explain some of these spiral patterns, due to the large pitch angle and highcontrast of the spiral arms in observations. We have carried out three dimensional (3-D) hydrodynamical simulationsto study spiral wakes/shocks excited by young planets. We find that, in contrast with linear theory, the pitch angleof spiral arms does depend on the planet mass, which can be explained by the non-linear density wave theory. Asecondary (or even a tertiary) spiral arm, especially for inner arms, is also excited by a massive planet. With a moremassive planet in the disk, the excited spiral arms have larger pitch angle and the separation between the primary andsecondary arms in the azimuthal direction is also larger. We also find that although the arms in the outer disk do notexhibit much vertical motion, the inner arms have significant vertical motion, which boosts the density perturbationat the disk atmosphere. Combining hydrodynamical models with Monte-Carlo radiative transfer calculations, we findthat the inner spiral arms are considerably more prominent in synthetic near-IR images using full 3-D hydrodynamicalmodels than images based on 2-D models assuming vertical hydrostatic equilibrium, indicating the need to model

46



observations with full 3-D hydrodynamics. Overall, companion-induced spiral arms not only pinpoint the companion’sposition but also provide three independent ways (pitch angle, separation between two arms, and contrast of arms) toconstrain the companion’s mass.

Accepted by ApJ


Abstracts of recently accepted major reviews

Physical processes in protoplanetary disks

Philip J. Armitage1

1 JILA, University of Colorado & NIST, Boulder, Colorado, CO 80309-0440, USA

E-mail contact: pja at jilau1.colorado.edu

This review introduces physical processes in protoplanetary disks relevant to accretion and the initial stages of planetformation. After reprising the elementary theory of disk structure and evolution, I discuss the gas-phase physics ofangular momentum transport through turbulence and disk winds, and how this may be related to episodic accretionobserved in Young Stellar Objects. Turning to solids, I review the evolution of single particles under aerodynamicforces, and describe the conditions necessary for the development of collective gas-particle instabilities. Observationsshow that disks are not always radially smooth axisymmetric structures, and I discuss how gas and particle processescan interact to form observable large-scale structure (at ice lines, vortices and in zonal flows). I conclude with diskdispersal.

Lectures given at the 45th Saas-Fee Advanced Course “From Protoplanetary Disks to Planet Formation”


47



Dissertation Abstracts

Mathesis of star formation from kpc to parsec scales

Guang-Xing Li

Max-Planck Institut fuer Radioastronomie

Scheinerstr. 1, D-81679 Mnchen, Germany

Address as of Nov. 2014: [email protected]

Electronic mail: gxli at usm.lmu.de

Ph.D dissertation directed by: Karl Menten, Friedrich Wyrowski, Pavel Kroupa

Ph.D degree awarded: Sept. 2014

In this thesis I present a series of studies aiming to understand the formation of stars from gas in the Milky Way.Generally speaking, I will progress from larger to smaller scales.

The kilo-parsec scale (∼ 103 parsec ∼ 1021 cm) is the scale at which dynamics of the molecular clouds is coupledto dynamics of the Milky Way disk. Here we present an observational study of molecular gas at 49.5◦ < l < 52.5◦

and −5.0 km s−1 < vlsr < 17.4 km s−1. The molecular gas is found in the form of a huge (>∼500 pc) filamentary gaswisp. It has a large physical extent and a velocity dispersion of ∼ 5 km s−1. The filamentary gas wisp is composedof two molecular clouds and an expanding bubble. The length of the gas wisp exceeds by much the thickness of themolecular disk of the Milky Way, and this is consistent with the cloud-formation scenario in which gas is cold prior tothe formation of molecular clouds.

Molecular clouds (1− 100 parsec) are the nurseries of the stars. There are many indications that molecular clouds areturbulence-dominated objects. However, it is not clear what role gravity plays. We propose a new method (G-virial)to quantify the role of gravity in molecular clouds. Our new method takes the gravitational interactions between allpixels in 3D position-position-velocity data cube into account, and generates maps of the importance of gravity in3D position-position-velocity space. With our method we demonstrate that gravity plays an importance role in theindividual regions in the Perseus and Ophiuchus molecular cloud, and find that high values of G-virial are reachedin cluster-bearing regions. We also demonstrate the capability of our method in finding regions and quantifying theproperties of the regions in the clouds.

Protostellar outflow (∼ 1 parsec) is a prominent process accompanying the formation of stars. In this work, wetheoretically investigate the possibility that the outflow results from interaction between the wind and the ambientgas in the form of turbulent entrainment. In our model, the ram-pressure of the wind balances the turbulent ram-pressure of the ambient gas, and the outflow consists of the ambient gas entrained by the wind. We demonstrate thatthe outflow phenomena can be naturally generated through this process, and discuss the potential usage of outflowsas a probes of the dynamical state of the turbulent molecular gas.

http://hss.ulb.uni-bonn.de/2015/3817/3817.htm

48

http://hss.ulb.uni-bonn.de/2015/3817/3817.htm

New Jobs

Postdoc position in millimeter observations of protoplanetary disks

One postdoc position is available in the group of Davide Fedele recently established at INAF-Osservatorio Astrofisicodi Arcetri (Florence, Italy).

The focus of the group of Davide Fedele is the physical structure and chemical composition of protoplanetary disks.The candidate will work on the analysis of submillimeter data with ALMA. Previous experience with submillimeterinterferometric data and/or disk modeling with thermo-chemical codes will be a plus in the evaluation. The positionwill be for an initial period of 2 years with a possible extension of one year dependent on performance. The expectedbeginning of the position is December 2015/January 2016. Application deadline is October 31 2015.

Applications should comprise a cover letter, a CV including publications, a concise statement of previous researchand research interests (max 2 pages), and 2 letters of recommendation. Evaluation will start on November 1st andcontinue until the position has been filled.

For inquires, instructions on how to apply, information about salary and benefits, please visit the webpages:

http://www.arcetri.astro.it/gare-e-concorsi/182-gare-e-concorsi/concorsi/945-2015-10-02-10-19-51

https://sites.google.com/site/davidefedele/research-1 and/or contact: [email protected]

Postdoctoral Position in Star Formation and Molecular Cloud studies

Applications are invited for a postdoctoral research position in the star formation group at the Astronomy Departmentat Yale University. We are seeking an astronomer with experience in reducing and analyzing radio/(sub)millimeterinterferometer data. The successful candidate will work with large-scale ( 2 square degree) CARMA molecular linemaps of nearby molecular clouds. The postdoc will be expected to help with the data reduction and analysis, leadresearch projects using the CARMA multi-line maps and collaborate with members of the international team.

Once combined with single dish data, these maps will probe the kinematics and structure of the molecular gas from7.2 pc down to 0.012 pc. The size and resolution of the maps will allow for unprecedented analysis of the large-scalestructure of molecular clouds. Research topics that may be conducted with these data include molecular cloud structureand kinematics, properties of cores and filaments, stellar feedback processes (outflow, winds, etc.), and turbulence.

Conveniently located between New York City and Boston, Yale offers a lively intellectual environment and accessto world-class astronomical facilities, including the Keck, Palomar and SMARTS telescopes. Yale is an institutionalmember of the SDSS-IV collaboration, and the postdoc may develop projects with these data.

Applications consisting of a cover letter, curriculum vitae, publication list, and a brief (2-3 page) description ofresearch interests and plans should arrive by December 18. 2015. Applicants should also arrange for three letters ofrecommendation to arrive by the same date. Email all materials, and have reference letters emailed to Kim Monocchi([email protected]). Inquiries about the position can be made to Hector Arce ([email protected]). Theanticipated start date is September 1, 2016, but earlier start dates are possible.

49

http://www.arcetri.astro.it/gare-e-concorsi/182-gare-e-concorsi/concorsi/945-2015-10-02-10-19-51

https://sites.google.com/site/davidefedele/research-1

Postdoctoral Researcher in Milky Way High Mass Star Formation

Postdoctoral Fellow - Astronomy (PHYS 15-0123)

The West Virginia University Research Corporation (WVURC) invites applications for a postdoctoral researcher inthe Department of Physics and Astronomy at West Virginia University (WVU). The applicant will work with Dr.Loren Anderson in studies of global Galactic massive star formation and HII regions. The main research project willbe to use a large catalog of Galactic HII regions to link Galactic and extragalactic star formation using studies of theGalactic HII region luminosity function, the Galactic star formation rate, and the star formation rate efficiency. Theproject will entail Green Bank Telescope, Very Large Array, and Australia Telescope Compact Array spectroscopicand continuum observations. Applicants with experience using these (or similar) facilities are especially encouragedto apply. A PhD in astronomy, astrophysics, or a closely related field is required. Knowledge of web programmingincluding database management is preferred.

WVU is a comprehensive land grant university with 29,000 students. WVU is classified by the Carnegie Com-mission on Higher Education as a Research-High Activity Institution. The Department of Physics and Astronomy(http://physics.wvu.edu) consists of 22 tenured and tenure-track faculty, one teaching assistant professor, 15 researchfaculty and postdoctoral researchers, 72 Ph.D. graduate students, and approximately 80 undergraduate physics ma-jors. The largest research areas are condensed matter physics, astrophysics, plasma physics, and physics education.WVU is located roughly 130 miles from the National Radio Astronomy Observatorys Green Bank Telescope in GreenBank, WV; many astrophysics research and outreach programs make use of the facilities in Green Bank.

Competitive salary and benefits package offered. For a complete job description and to apply for this position, pleasevisit http://hr.research.wvu.edu and click on the View Jobs link. Qualified applicants should submit a cover letter,statement of research interests (up to 2 pages), curriculum vitae, and contact information for three references as partof the application process. For questions or additional information, contact Prof. Loren Anderson at 304-293-4884or [email protected]. The screening process will begin on November 1, 2015 and will continue until theposition is filled.

The University community of Morgantown offers plentiful educational opportunities as well as recreational outlets, iswithin easy driving distance of Pittsburgh, PA, and is about 200 miles (3.5 hours driving) northwest of Washington,D.C. WVURC is an AA/EOE/Minorities/Females/Vet/Disability/E-verify compliant employer.

Postdoctoral position in the study of star formation or outflow modeling

Applications are invited for a postdoctoral position in the observational study of massive star formation or MHDmodeling of (proto-)stellar outflows at Chalmers University of Technology in Gothenburg, Sweden. The 2-year positionwill be within the research group of Wouter Vlemmings. This group focusses on radio, millimeter and/or sub-millimeterwavelength observations of evolved stars and star forming regions with instruments such as ALMA, SMA, JVLA,eMERLIN and APEX. The postdoc will work on related topics and will also be able to carry out their own researchin collaboration with affiliated group members.

The successful candidate will join a research group with close ties to the Nordic ALMA Regional Center (ARC) node.He/She will have access to advanced radiative transfer modeling tools and the possibility to develop MHD simulations.The postdoc will work mainly at Onsala Space Observatory, where Chalmers hosts the Swedish National Facility forRadio Astronomy.

A PhD in astrophysics is required at the start of the employment (expected to be early 2016). Experience with(massive) star formation, interferometry or MHD simulations would be an asset. The application deadline is Nov 2nd2015. For application details please follow the link to the electronic submission form at the following page:

http://www.nordic-alma.se/local-links/my-research/projects

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http://www.nordic-alma.se/local-links/my-research/projects

Postdoctoral position in Astrochemistry and Star/Planet formation

The Center for Astrochemical Studies (CAS; http://www.mpe.mpg.de/CAS) at the Max Planck Institute for Ex-traterrestrial Physics (MPE) in Garching (near Munich), Germany, invites applications for a Postdoctoral position inastrochemistry and observational/theoretical star and planet formation. The overall aim of the project is to studystar and planet formation, from the assemblage and earliest phases of pre-stellar cloud cores to the formation and evo-lution of protoplanetary disks, with links to our Solar System, using molecular lines and dust continuum observationsas tools to unveil the physical and chemical evolution. This will be done by merging astrochemical with (magneto-)hydro-dynamical models and constraining them with high sensitivity and high angular/spectral resolution observationsvia the use of radiative transfer codes. Researchers with experience in theory and/or observations of star and planetforming regions are encourage d to apply.

The flexible starting date could be as early as Spring 2016, for 2 years guaranteed with the possibility of extensionto up to five years and further career within MPE. The salary is paid at German civil service rates (TVoD-Bund)depending on your post-doctoral experience.

Applicants should have a PhD in astronomy or related field before starting. The post comes with generous travelallowance. Please send a letter of application, a brief description of research interests, a curriculum vitae includingbibliography, and three letters of reference by Nov. 15th, 2015 to:

Paola Caselli ([email protected])

Later applications may also be considered in case the post is not filled until Dec. 15th, 2015.

The MPE encourages applications from women, minorities and disabled persons.

51

Meetings

2nd Announcement: From Stars to Massive StarsWed. 6th - Sat. 9th April 2016

University of Florida, Gainesville, FL, USA

http://conference.astro.ufl.edu/STARSTOMASSIVE/

From Stars to Massive Stars - Connecting our understanding of massive star & star cluster formation through theuniverse. Contact: florida.starformation @ gmail.com

This conference will bring together researchers from star formation, star cluster evolution and massive star communitiesto share recent research results and help motivate future projects to improve our understanding of these processesand phenomena. The meeting comes at a time when many exciting results are appearing from surveys of our Galaxysstar-forming regions along with detailed follow-up from facilities such as ALMA and SOFIA. Utilization of JWST andTMT-class telescopes is on the horizon, which, along with full-ALMA, will allow unprecedented studies of massive starand star cluster formation across a wide range of cosmic environments. Properties of individual stars and protostarscan be determined to build up an accurate statistical census of the star formation activity in entire giant molecularclouds and their star-forming clumps, thus probing the questions: what drives massive star and star cluster formationand how does it proceed in different environments such as the local solar neighborhood, dwarf galaxies, dense starburstregions, around supermassive black holes such as in Galactic center region, and at the very highest redshifts? Withincreasing computational resources and more sophisticated numerical modeling, theoretical and numerical models arecatching up to try to explain these observations.

Specific science topics include:

1) Initial Conditions for Massive Star and Star Cluster Formation2) Astrochemistry in Massive Star and Star Cluster Formation3) Accretion to Massive Protostars: Infall Envelopes and Disks4) Outflows from Massive Protostars5) Hypercompact and Ultracompact HII Regions6) The Multiplicity, Clustering and Cluster Environment of Massive Star Formation and Young Massive Stars7) Similarities and Differences of Low-, Intermediate- and High-Mass Star Formation and Young Stars8) Feedback from Massive Star and Star Cluster Formation9) Massive Star and StarCluster Formation in Galactic Centers and Starbursts10) Massive Star and Star Cluster Formation at Low-Metallicity and at High Redshift11) The Initial Mass Function and Stellar Evolution ofMassive Stars12) The Initial Cluster Mass Function and the Early Evolution of Star Clusters

The conference will be held at the University of Florida in Gainesville, located within 2 hours drive from Orlando,Tampa, Jacksonville, St. Augustine, and the Atlantic and Gulf Coasts. The weather in April is generally dry, sunnyand warm.

Estimated costs: We expect the registration fee to be less than $200. Hotel rooms in the conference block will beabout $100 to $130 per night. Conference activities will start with a reception on Tue. 5th April and there will be afull day of science presentations on the Sat. 9th April, so plan for a 5 night stay. Some financial support, especiallyfor graduate students and junior researchers is available - please indicate if you want to be considered for this supportin the comments section of the registration form.

If you are interested in attending the conference, please register and submit an abstract by 1st Dec. 2015 for consid-eration by the SOC.

Best regards,

Jonathan Tan & the SOC

52


Summary of Upcoming Meetings

Exchanging Mass, Momentum and Ideas: Connecting Accretion and Outflows in Young Stellar Objects27 - 29 October 2015 Noordwijk, The Netherlandshttp://www.cosmos.esa.int/web/accretion-outflow-workshop

Extreme Solar Systems III 29 November - 4 December 2015 Hawaii, USAhttp://ciera.northwestern.edu/Hawaii2015.php

Protoplanetary Discussions7 - 11 March 2016, Edinburgh, UKhttp://www-star.st-and.ac.uk/ppdiscs

From Stars to Massive Stars6 - 9 April 2016, Gainesville, Florida, USAhttp://conference.astro.ufl.edu/STARSTOMASSIVE/

Resolving planet formation in the era of ALMA and extreme AO16 - 20 May 2016, Santiago, Chilehttp://www.eso.org/sci/meetings/2016/Planet-Formation2016.html

Diffuse Matter in the Galaxy, Magnetic Fields, and Star Formation - A Conference Honoring theContributions of Richard Crutcher & Carl Heiles23 - 26 May 2015, Madison, USAno URL yet

The 19th Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun6 - 10 June 2016 Uppsala, Swedenhttp://www.coolstars19.com

Cloudy Workshop20 - 24 June 2016 Weihai, Chinahttp://cloudy2016.csp.escience.cn/dct/page/1

EPoS 2016 The Early Phase of Star Formation - Progress after 10 years of EPoS26 June - 1 July 2016, Ringberg Castle, Germanyhttp://www.mpia.de/homes/stein/EPoS/2016/2016.php

Star Formation in Different Environments25 - 29 July 2016 Quy Nhon, Viet Namwebsite to be announced

Star Formation 201621-26 August 2016 Exeter, UKhttp://www.astro.ex.ac.uk/sf2016

Other meetings: http://www1.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/meetings/

53

http://www.cosmos.esa.int/web/accretion-outflow-workshop

http://ciera.northwestern.edu/Hawaii2015.php

http://www-star.st-and.ac.uk/ppdiscs


http://www.eso.org/sci/meetings/2016/Planet-Formation2016.html

http://www.coolstars19.com

http://cloudy2016.csp.escience.cn/dct/page/1

http://www.mpia.de/homes/stein/EPoS/2016/2016.php

http://www.astro.ex.ac.uk/sf2016

http://www1.cadc-ccda.hia-iha.nrc-cnrc.gc.ca/meetings/

Short Announcements

Launch of the AstroChemical Newsletter

We are announcing the launch of the AstroChemical Newsletter, a monthly compilation of recently accepted publica-tions and announcements in the field of astrochemistry (astrophysical observations and modeling as well as theoreticaland experimental chemical-physics related to astronomical environments).

You can subscribe to the newsletter and submit abstracts by going to the AstroChemical Newsletter website:http://acn.obs.u-bordeaux1.fr/

You can also share your latest astrochemistry news on the AstroChemical Newsletter Facebook page:https://www.facebook.com/AstrochemicalNewsletterand follow @AstroChemNews on Twitter.

Moving ... ??

If you move or your e-mail address changes, pleasesend the editor your new address. If the Newsletterbounces back from an address for three consecutivemonths, the address is deleted from the mailing list.

54

http://acn.obs.u-bordeaux1.fr/

the star formation newsletterthe big diﬃculty are the high shock speeds required to ex-plain...

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