molecules in high redshift galaxies as probes of star formation and galaxy evolution alain omont...
Post on 22-Dec-2015
213 views
TRANSCRIPT
Molecules in high redshift galaxies as probes of star formation and galaxy evolution
Alain Omont (IAP, CNRS and Université Paris 6)
OUTLINEMolecules in high redshift galaxies Molecules in high redshift galaxies
as probes of star formation and galaxy evolutionas probes of star formation and galaxy evolution
General Features - Molecules in the ISM of galaxies - Molecules at high redshift Millimeter emission of molecules at very high redshift (PdBI)
- CO and the structure of starbursts in SMGs
- Mm follow up of the Spitzer heritage
- CO in high z QSOs and the MBH/Mspheroid relation
PAHs as tracers of starbursts
H2 as tracer of shocks and cooling of warm gas
Prospects (ALMA, etc.)
Omont 2007, Rep. Prog. Phys. 70, 1-78 Solomon & Vanden Bout 2005 ARAA 43, 677
- Local ULIRGs (Yu Gao) - Molecular absorption lines (mm, radio, UV) at high z
- Lensing of high-z molecular lines
- * Special features of interstellar chemistry at high redshift Other molecules than CO (and H2 and PAHs)
- * Evolution of nucleo-synthesis through molecular isotopes - Host galaxies of the most distant QSOs (Ran Wang)
- * Molecular outflows and AGN feedback
- H2O mega-masers
- Possible variation of fundamental constants measured with molecular lines: me/Mp through UV H2 lines, through OH lines- Etc.
Important topics NOT to be addressed(* = still poorly documented)
Molecules are essential ingredient of the interstellar medium
• Normal molecular gas: cold (~10-100K) and dense (~103-105 cm-3)
Various steps of star formation:- Giant Molecular Clouds- Accretion disks- Molecular outflows- Photo-Dissociation Regions and Compact HII Regions- Supernova remnants
• Warm molecular gas: - Shocks - (+ UV or X fluorescence, stellar winds, etc.)
Molecules are essential ingredient of the interstellar medium
Rich molecular diagnosis
• VelocityVelocity fields in dense, obscured gas dynamicsdynamics: rotation, outflows (inflows), merging, shocks
• MassMass of molecular gas. Dynamical massDynamical mass of the galaxy
• TemperatureTemperature probe: Molecular ladder excitation through collisions (vs radiative processes): CO, NH3, etc.
Other excitation (shocksshocks, UV…) and coolingcooling processes
• ChemistryChemistry processes: formation/destruction: UV, Cosmic Rays, shocks, grains, X-rays, etc.
• Abundances Abundances of elements and isotopes
General Features at high redshift
• z > (0.5)-1 6…. (mostly ~2) - Cosmic times
• D2 distance fading: ~105 from nearby galaxies to local ULIRGs (z~1). Another factor ~200 to z=2
Rudimentary informationRudimentary information
• Exceptional Exceptional objects. Peak of starbursts and AGN
• Metallicity/UV: harshharsh for molecules
Millimeter CO lines are by far the best tracer of molecular gas
• H2 is hardly observable in cold gas
- IR lines are not excited and forbidden
- Absorption UV lines are too extincted
-------------------------
--------------------------
-------------------------- -
---------------------------
----------------------------
----------------------------
----------------------------
---------------------------
--------------------------- --------------------------- ---------------------------
J = 10 275 K
J = 9 250 K
J = 8 180 K
J = 7 140 K
J = 6 105 K
J = 5 75 K
J = 4 50 K
J = 3 30 K
J = 2 15 KJ = 1 5 KJ = 0 0 K
Rotational CO lines
1.3mm 230GHz 2.7mm 115GHz
520µm 576GHz
260µm 1152GHz
Redshifted lines =0 /(1+z)
Millimeter CO lines are by far the best tracer of molecular gas
• H2 is hardly observable in cold gas
- IR lines are not excited and forbidden - Absorption UV lines are too extincted
• CO millimeter lines are: - the strongest millimeter lines
- free from dust extinction
- observable with heterodyne high velocity resolution
- observable with high angular resolution with mm interferometers
- easy to excite in cold gas
- providing a good diagnostic of TK through multi-line studies
- roughly proportional to the mass of H2
- available in 3mm (1.3mm) atmospheric band at practically any redshift
- easy to observe at high z through an « inverse K-correction »
-------------------------
--------------------------
-------------------------- -
---------------------------
----------------------------
----------------------------
----------------------------
---------------------------
--------------------------- --------------------------- ---------------------------
J = 10 275 K
J = 9 250 K
J = 8 180 K
J = 7 140 K
J = 6 105 K
J = 5 75 K
J = 4 50 K
J = 3 30 K
J = 2 15 KJ = 1 5 KJ = 0 0 K
Rotational CO lines
1.3mm 230GHz 2.7mm 115GHz
520µm 576GHz
260µm 1152GHz
« Inverse K-correction » for CO lines
Redshifted lines = 0 /(1+z)
Line J ~ 1+z redshifted into the 3 mm best atmospheric band
Line luminosity proportional to J3
strong increase of the 3mm line, almost compensating for the distance2 decrease
Millimeter CO lines are by far the best tracer of molecular gas
• H2 is hardly observable in cold gas - IR lines are not excited and forbidden - Absorption UV lines are too extincted
• CO millimeter lines are: - the strongest millimeter lines
- free from dust extinction- observable with heterodyne high velocity resolution- observable with high angular resolution with mm interferometers
- easy to excite in cold gas - providing a good diagnostic of TK through multi-line studies - roughly proportional to the mass of H2
- available in 3mm (1.3mm) atmospheric band at practically any redshift- easy to observe at high z through an « inverse K-correction »
• However,
- complex CO line formation uncertain MH2
- limited angular resolution uncertain Mdyn
- limited current sensitivity massive objects = Submm Galaxies (SMGs)
Molecular gas in Sub-Millimeter Galaxies (SMG)
From the heritage of SCUBA
To updated IRAM-PdBI
Waiting for ALMA
5
SMGs: strongest starbursts in the UniverseEssential steps of star formation in massive galaxies at z >~ 2
Revealed by SCUBA surveys at 850µm (+ MAMBO at 1.2mm AzTEC, LABOCA, BOLOCAM)
Easy detection of dust FIR emission through « inverse K-correction », same flux at ~1mm from z ~ 0.5 to 10
At least ULIRGs 1012 Lo Numerous ~0.1-0.3 per arcmin2
Star Formation Rate SFR > 100 Mo/yr
Account for a significant fraction of submm background
Most exceptional HLIRGs 1013 Lo, 1000 Mo/yr nothing equivalent in the local Universe
Giant starbursts at the peak of star formation, z ~ 2-3 1-4, in massiveproto-elliptical galaxies
Dissecting SMGs through mm CO lines at IRAM-PdBI
• (Very) Large program at the IRAM Plateau de Bure millimeter interferometer (PdBI) (Genzel, Ivison, Neri, Tacconi, Smail, Chapman, Blain, Cox, Omont, Bertoldi, Greve et al.)
• -30 SMGs with z~2-3 spectroscopic redshifts from radio positions (Chapman, et al.)
• Detection and velocity profiles of CO(3-2) and (4-3) lines for 22 SMGs (Neri et al. 2003, Greve et al. 2005, Tacconi et al. 2006, Smail et al. in prep.).
• Subarcsecond resolution imaging in progress (Tacconi et al. 2006, 2008, and in prep.)
• Parallel programs for HST imaging and high resolution radio imaging with MERLIN
• Key goals - Physical properties and evolution of the SMG population - How SMGs fit in general picture of galaxy evolution and formation
(Greve et al. 2005; Neri et al. 2004)
Detection with low angular resolutionHigh angular resolution: Tacconi+
22 radio-detected submm galaxies with known optical/near-IR redshift detected in CO (March 2008)
1<z<3.5
Variety of profiles: 500-1000 km/s
SFR 500 - >1000 Msun/yr
MH2 ~ 3x1010 Msun
Mdyn ~ 1011 Msun
SMM J02396-0134 SMM J02399-0136 SMM J04431+0210
SMM J09431+4700 SMM J13120+4242 SMM J14011+0252
SMM J16368+4057 SMM J16359+6612 SMM J16366+4105
SMM J16371+4053 ERO J16450+4626 SMM J22174+0015
CO Survey of submm Galaxies
(from P. Cox)
High angular resolution CO mapping at PdBI
Example of mapping CO in an SMG at PdBICase of an unresolved ~1kpc rotating disk
(2008)
Examples of mapping CO in SMGs at PdBISpatial and Kinematic Evidence for Mergers
Double or multiple knots, with complex, disturbed gas motions
Tacconi et al. 2008
• High CO detection rate, close to 100% with current PdBI sensitivity
• Large fraction are resolved with subarcsecond resolution (2/3 are resolved in the radio with 0.3’’ MERLIN beam)
• Mm lines of the molecular ISM, are unique to trace dynamical masses. (Also large stellar masses > 1011Mo)
• SMGs are short-duration (~100 Myr) maximum starburst events in the evolution of a major gas-rich merger of massive galaxies.
• Different combinations of ordered disk rotation and merger driven random motions and inflows
• The high surface densities in SMGs are similar to compact quiescent galaxies in the same redshift range and much higher than in local spheroids.
Current conclusions of PdBI CO survey of SMGs
The Spitzer Heritage for Molecules in Galaxies
Routine detection of PAHs at z~2 PAHs are universal (in starbursts) at high z
24µm bright SMGs and CO detection
Massive detection of H2 rotational lines
11
PAHs at highy redshift as tracers of starbursts
PAHs are known to be an important component of the ISM
Polycyclic Aromatic Hydrocarbons and related species are nano-particles from ~50 to a few 102 atoms, intermediate between conventional dust and molecules
They are not individually identified, but display characteristic IR vibration features from C-H bonds and 2D C-lattice
Orion
PAHs at highy redshift as tracers of starbursts
PAHs are known to be an important component of the ISM
Polycyclic Aromatic Hydrocarbons and related species are nano-particles from ~50 to a few 102 atoms, intermediate between conventional dust and molecules
They are not individually identified, but display characteristic IR vibration features from C-H bonds and 2D C-lattice
It is known from ISO that their bands dominate the mid-IR spectrum of galaxies. They are excited from UV fluorescence, and are thus interesting tracers of star formation
The sensitivity of Spitzer InfraRed Spectrometer (IRS) at ~20-30µm allows routine detection of PAHs in 24µm-bright ULIRGs: z~1-2.5, in redshifted 6 to 11µm bands, especially 7.7µm
PAH features are known to be relatively weaker in AGN, compared to hot dust continuum. PAHs are thus a good discriminant between starburst and AGN in high-z ULIRGs
mJy
Highest z, z=3.01 Huang+07
St
24µm bright z~2 starbursts Yan et al. 2007
PAHs are universal in starbursts at high z
Several 10^2 Spitzer/IRS spectra of 24µm sources
PAHs are universal in starbursts at high z
Several tens of SMGs at z~2
SCUBA-MAMBO SMGsValiante et al. 2007
Spitzer selected
SMGs
Average obs. spectra
(and templates)
Huang+ in prep.
Mid-IR spectral features (PAHs and silicates) are detected up to z=3
Hundreds of high-z spectra:
• PAHs emission bands mostly in starbursts
• Silicates in absorption 10µm (+18µm) in compact sources: AGN (+ starbursts)
• Composite spectra are frequent
• PAH features are weaker in AGN, but frequent, including classical bright high-z QSOs (Lutz et al. 2008)
Yan et al. 2007
Questions--------------
Spitzer data are still very incomplete, many unpublished; their analysis is thus begining
PAH fraction and diagnostic
Modelling observed spectra (in relation with gas properties):
In starbursts: various types; environment
In AGN:Central regionsAbsorption/emission of the host galaxy
Winds: AGN/starbursts
Spitzer 24µm-bright SMGs
Only ~500 SMGs provided by SCUBA/MAMBO surveys( <~ 0.5-1 deg2) AzTEC
Waiting for SCUBA2, Herschel, much larger (x>10) samples already exist in Spitzer wide field surveys, but difficult to identify
However, easy identification of a special subclass of z~2 SMGs, - large PAH/FIR ratio (strong 24µm) - large stellar mass (1.6µm-rest bump in SED not AGN-dominated) - ~50deg-2, in particular in SWIRE survey: 50 deg2
With MAMBO/IRAM we have confirmed they are SMGs by detecting
~50-60 SWIRE z~2 starburst ULIRGs/HLIRGs at 1.2mm (Lonsdale+ 2008, Fiolet+ in prep.
Younger+ in prep.)
14
CO detection in Spitzer 24µm-bright high-z ULIRGs
• Spitzer 24µm-bright SMGs are obvious targets for CO search, andcomparison with classical SMGs
• However, because of limited mm bandwidth, need for optical spectroscopic redshifts: difficult in ‘redshift desert’ z~1.7-2.0: only a few redshifts determined
• CO search in IRS sources of Yan et al. in progress at PdBI (Tacconi+ in prep., Fiolet+ in prep. + Yan, Lutz, Fiolet, Cox, Sajina, Omont et al. )
Easy detection 8/8 observed sources: - not only on PAH-dominated sources - but on ‘composite’ AGN/starbursts, and even pure silicate- absorption spectra (including radio loud ones)
MIPS16144 – Integrated CO 3-2 Emission
‘PAH’ source, Mambo flux=2.930.56, z=2.1340 MHz spectral smoothing, rms=0.32 mJy/beamC-configuration
strong PAHs
strong MAMBO 1.2m flux (2.9mJy)
strong CO
L. Tacconi in prep.
Srong 10µm silicate absorption
Narrow CO line, radio loud
Fiolet et al. in prep.
Weak 1.2mm MAMBO
Broad CO line
CO in high z QSOs and the MBH/Mspheroid relation
• High continuum 1.2mm detection rate of high-z luminous QSOs (55/200) Omont +.1996, Carilli + 2001, Omont+ 2001, Omont + 2003, Bertoldi+ 2003, Beelen 2004, Wang+ 2007,2008
strong starburst in their host galaxies (practically all the ‘SMGs’ identified at z>4) • CO has been detected in at least 18 high-zQSOs with IRAM-PdBI
• CO linewidth provides Mdyn x sin i
• MBH may be estimated from broad optical lines, or Lbol
• Coppin et al 2008 almost doubled the number of high-z QSOs with CO and MBH
CO(3-2) in J1409+5628
IRAM-30m + MAMBO camera
Beelen+ 2004
Six z~2 QSOs (i=20°) Coppin et al. 2008 Nine z~2-6 QSOs Shields et al. 2006
The ratio MBH/Msph of bright QSOs at z>~2 is larger than the local relation by an order of magnitude
H2 at high redshift
H2 UV absorption lines in damped Lyman-α systems of quasars
Emission of H2 mid-IR rotation lines from warm molecular gas of various origin
Breakthrough of (ISO and) Spitzer on H2 emission in local sources (up to z~0.3)Verma+ 2005, Rigopoulou+ 2002, Valentin & van der Werf 1999, Haas+ 2005: Various ISO resultsRoussel et al. (2007) SINGS nearby galaxiesHigdon et al. (2006) Local ULIRGsOgle et al. ( 2006) Local radio galaxiesJohnstone et al. (2007) Cooling-flow clustersAppleton et al. (2006) Galaxy-size shock in Stephan’s QuintetEgami et al. (2006) IR-luminous brightest galaxy of Zwicky cluster 3146 (z=0.3) Many more unpublished results
However, no H2 rotation line has yet been confirmed at high z
H2 at high z is a major target for future space missions: JWST, SPICA, H2EX, etc.
H2 cooling is fundamental for the formation of the first galaxies from primordial gas H2 (and HD) chemistry in primordial collapses is included in every model of formation of first galaxies
The promises of upgraded IRAM-PdBI (in 2007 PdBI has increased sensitivity by >~2 and baseline by ~2)
Further gain by 2009: larger bandwidth and more bands.
Sensitivity gain in continuum vs 2006 ~4-7 (20-50 in time!)
(+ multi-line, uncertain redshifts, extended baseline…)
Ambitious goals in high-z galaxies in pre-ALMA area:
- Several large programs on SMGs, Spitzer galaxies, AGN, radio sources, etc.
- More exploration of weaker sources: LBGs, BzKs, AGN, etc.
- Multi-line studies
- Deep and ultra-deep fields. Identification of z>5 SMGs
- Systematic follow-up of Herschel (and SCUBA2 sources)
- Etc.
20
The promises of upgraded IRAM-PdBI (in 2007 PdBI has increased sensitivity by >~2 and baseline by ~2)
Further gain by 2009: larger bandwidth and more bands. Sensitivity gain in continuum vs 2006 ~4-7 (20-50 in time!) (+ multi-line, uncertain redshifts, extended baseline…)
Ambitious goals in pre-ALMA area: - Several large programs on SMGs, Spitzer galaxies, AGN, radio sources, etc. - More exploration of weaker sources: LBGs, BzKs, AGN, etc. - Multi-line studies - Deep and ultra-deep fields. Identification of z>5 SMGs - Systematic follow-up of Herschel (and SCUBA2 sources) - Etc.
Longer termLonger term::
Further bandwidth increase, up to 16 GHz (correlator)
Multi-beam receivers?
Double the number of antennas?
Ultimate goal:
Make the IRAM Interferometer the leading instrument on the northern hemisphere with 30-50% ALMA sensitivity in the mm range
ALMA50 12m-antennas 6 times the current PdBI collecting areaExcellent site, full submm capabilities (compact array) breakthrough
Comprehensive studies of high-z dusty starbursts in ALMA ultra-deep fields
Earliest starbursts in the Universe with deep fields, ‘gravitational telescopes’ and ALMA-JWST combined projects
Mapping all kinds of star-forming galaxies at all z: dust and mainly CO, C+ and CI lines structure and physical conditions
Blind z determination from CO. Multi-line detections in strong sources
Interstellar chemistry at all redshifts, including isotopomers,
Absorption lines with thousands of background sources ISM in standardgalaxies
Etc.
First ALMA Science in 2010!
JWST MIRI/JWST will have orders of magnitude improvements in sensitivity, spatial and/or spectral resolution compared with Spitzer synergy with ALMA
PAHs and H2 in various types of high z galaxies
SKA (when high bands are implemented)
Will be complementary to ALMA for studying the cold gas, detecting OH and H2O mega-masers and z>2 low-J lines of CO and other molecules
Herschel Too small collecting area vs ALMA (/500!) for high-z molecules
But will detect 104’s of SMGs in wide surveys with full SEDs, LFIR and SFR
For follow up at PdBI and ALMA
Prospects
Herschel bands and SMG SEDs
• Galaxy evolution
- Major evolution steps of the structure and star formation of massive galaxies -The first ULIRGs/HLIRGs at z >5-7- Physics of the most extreme starbursts- Physics of massive galaxy mergers- What is the importance of very cold molecular gas- Special features of interstellar chemistry at high redshift- Evolution of nucleo-synthesis through molecular isotopes- Early galaxy clustering at z>2- Galactic outflows in SMGs- Galaxy size shocks: accretion shocks; cooling flows; galaxy and cluster collisons, - Cooling of primordial gas in first (proto-)galaxies through H2 and HD
• AGN-galaxy connection and BH growth - Parallel evolution of AGN and starbursts. Host galaxies of obscured AGN.- Molecular outflows and AGN feedback. Molecules associated with jets of radio galaxies- Origin of the MBH- relation. Evolution with redshift - Host galaxies of the first super massive black holes - Physics of the central ISM in AGN host galaxies; molecular torus and accretion disk: H2O mega-masers, etc.
• Fundamental physics and cosmology- Possible variation of fundamental constants measured with molecular lines: me/Mp through UV H2 lines, through OH lines- H0 determination from H2O mega-masers- Angular narrow-band correlations in CMB
• Interstellar dust and nano-particules- PAH properties in various galactic environments and redshifts- (Origin of Diffusse Interstellar Bands)
20 Questions to be addressed by observations of molecules in galaxies (at high z)
z Dphot (Gpc)
1000
--------------------
20
12
--------------------
z= 6
--------------------
z=2 -------------------
z=0.5 --------------------
z=0
~ 300 million
~ 3.5 billion
z >~ 20-30Dark agesNo stars, no galaxies
z ~ 6 – 15 ?Reionization - First galaxies - First QSOs
z ~ 4 – 7 :Current frontier- Galaxy and Black-Hole early assembly- End of reionization
z ~ 1.5 -4: - Peak of star formationin massive elliptical galaxies- Peak of QSO activity
z ~ 0.5-1.5 : Final phase of active SF peak in spiral galaxies
Cosmic Times
Molecules are essential ingredient of the interstellar medium
Cooling through molecular lines
- Cold molecular gas: CO
- Warm: H2, H2O, CO primordial gas: H2, HD
- (Heating through PAH photo-ionization)
Molecular masers:
OH, H2O Mega-masers
Connection with interstellar grains building molecular complexity
- H2 formation on grains
- Other chemical processes on grains. Accretion/desorption
- Polycyclic Aromatic Hydrocarbons (PAH) and related species
- Building molecular complexity pre-biotic molecules?
Distance fading
Flux proportional to 1/DL2 (DL = Luminosity Distance)
very large factor
“nearby” “local” high-zgalaxies ULIRGs, QSOs SMGs, QSOs
Redshift 0.001 0.1 2DL
2(Gpc2) 2 10-4 0.2 40
[But additional factor when observing at fixed frequency emission at 0 = (1+z)]
General features at high z
Prospects: SMGs in wide Herschel surveys
Full SEDs, LFIR and Star Formation Rate
Detection of tens of thousands SMGswith full SEDs at maximum of FIR emission
LFIR (and Tdust) Star formation rate Stacking analysis with Spitzer, radio, etc.
Star formation @ z = 2.5
▪ Submm bright Galaxy Population MSB ?
▪ Single or merging LIRGs ?
Greve et al. 2005Greve et al. 2005
Tacconi et al. 2007
(from P. Cox)
Gain in Sensitivity / TimeGain in Sensitivity / Time
FrequencyFrequency 110 GHz110 GHz 140 GHz140 GHz 230 GHz230 GHz 345 GHz345 GHz
LineLine 1.7 / 31.7 / 3 2.7 / 72.7 / 7
Cont 2 GHzCont 2 GHz 2.3 / 52.3 / 5 3.7 / 143.7 / 14
Cont 4 GHzCont 4 GHz 4.5 / 204.5 / 20 7.1 / 507.1 / 50
2008
2008
2007
2007
2007 2008 2009 2010 2011 2012 =>
NG-PdB 3
NG-PdB 4
4GHz corr
4GHz corr
NG-PV NG-PV
HEMT-PV HEMT-PV
HERA xer HERA xer
3mm Arr 3mm Arr 3mm Arr
Bolo Bolo Bolo Bolo
SHERA SHERA SHERA SHERA
2SB/8GHz
2SB/8GHz 2SB/8GHz 2SB/8GHz
16Ghz corr 16GHz corr
16GHz corr
50ch FX 50ch FX
The Current 5-year Plan
Early CO detections ….. and their improvements
CO has been detected at high z since 15 yearsFIRAS 10214, Cloverleaf, BR1202-0725, APM 08279+5255, etc.
Significative improvements especially with new capabilities of PdBI
E.g.
- New map of CO(5-4) in BR1202-0725 this rules out lensing andconfirms 2 HLIRGs at ~30-50kpc
- Multiple CO Lines
1.2mm dust map CO(5-4) 3mm spectra
Absorption/emission
- Emission (lines) is affected by factor 1/DL2 exceptional objects
but strength of absorption lines independent of DL “normal” galaxies
- Absorption in many mm lines in a very few systems provide a glimpse at
molecular gas in « ordinary » galaxies at z ~0.2-0.9 (Wiklind & Combes)
Gravitational Lensing Amplification allows gain up to 50
General features
(Kneib et al.) z=2.5 J=3-2 (30K)
APM 08279+5255 (z=3.9) : very hot CO SMM J16359 + 6612 : weak galaxy, multi-image
(Weiss et al.)
J=11-10 (300K)