nrao socorro 05/2009 radio continuum studies of massive protostars peter hofner new mexico tech...
TRANSCRIPT
NRAO Socorro 05/2009
Radio Continuum Studiesof Massive Protostars
Peter Hofner
New Mexico Tech & NRAO
NRAO Socorro 05/2009
Collaborators
E. Araya NRAO/UNM
S. Kurtz, L. Rodriguez CRyA-UNAM
M. Goss, D. Shepherd NRAO
H. Linz MPIA
R. Cesaroni Arcetri Observatory
C. Anderson NMT
NRAO Socorro 05/2009
Outline
• Introduction: DR21
• VLA Observations of Massive Protostars: Jets Photoevaporating Disks Accretion Shocks
• IR and X-Ray Counterparts
NRAO Socorro 05/2009
Cygnus at 5 GHz
Downes & Rinehart 1966
85 ft single dish telescope at Fort Davis, TX
5GHz, FWHM: 10.8'
Many discrete sources: thermal spectra
NRAO Socorro 05/2009
Cygnus at 5 GHz
Downes & Rinehart 1966
85 ft single dish telescope at Fort Davis, TX
5GHz, FWHM: 10.8'
Many discrete sources: thermal spectra
DR21
NRAO Socorro 05/2009
Compact HII Region
Ryle & Downes 1967: Cambridge 1 mile Interferometer:First Aperture Synthesis, 1.4 GHz, FWHM: 30"
DR21: the first compact HII region
NRAO Socorro 05/2009
Ultracompact HII Regions
Harris 1973Cambridge 5 km Interferometer5 GHz, FWHM: 3"
Component D: Cometary UCHII RegionEM= 8.2x107 pc cm-6, ne=6.5x104 cm-3
Central star: B0
NRAO Socorro 05/2009
Surveys for Massive Protostars
Selection Criteria: FIR color L > 103 L
dense, hot molecular gas ‘absence’ of radio continuum
> 200 candidates 90 % detection rate of outflows (CO) evolutionary stage of candidates ?
Pankonin et al. 2001, Araya et al. 2005, Palla et al. 1991, Molinari et al. 1998, 2000Sridharan et al. 2002, Beuther et al. 2002
NRAO Socorro 05/2009
Radio Continuum Emission
• Signposts for positions of massive protostars
• Emission mechanisms: How does the intensity of radio continuum relate to overall luminosity ? Evolutionary state
• Multiplicity/Cluster vs Accretion Disks
NRAO Socorro 05/2009
Radio Continuum Emission Models
• Dust emission• Ionized accretion flows• Photoevaporating disks• Accretion shocks• H, H2 – e- free-free • Spherical or Equatorial Winds• Shocks in flows• Jets
NRAO Socorro 05/2009
Deeply Embedded Sources
Molecular Clumps: Size = 1 pc NH = 1023 cm-2
Hot Molecular Cores: Size = 0.1 pc NH 1025 cm-2
Predicted Extinction:AV > 1000
cm observations ! Cesaroni et al. 2005
NRAO Socorro 05/2009
IRAS 20126+4104
Distance: 1.7 kpc
Luminosity: 1.3 104 L
HMC: T 200 K nH2
7 108 cm-3
Bipolar Molecular Flow: 2 N-S in CO
30 NW-SE in HCO++
Velocity gradient Flow Disk ?
Cesaroni et al. 1999
+
++++
+ 44 GHz CH3OH Masers
NRAO Socorro 05/2009
IRAS 20126+4104
Hofner et al. 2007
VLA A-configuration X-band
Where is the massive protostar ?
a) In between N1 and N2
b) Near peak of N1
c) Somewhere else
NRAO Socorro 05/2009
Thermal dust at 3 & 1.3 mm extended dust disk 2.5 M
(1500 AU)
Ionized gas with density gradient at 3.6, 1.3 & 0.7 cm (< 50 AU) associated with outflow
Limit on Disk Mass: < 0.8 M
(< 50 AU)
IRAS 20126+4104
Hofner et al. 2007
NRAO Socorro 05/2009
IRAS 20126+4104
Ionization equilibrium: N1 and N2 not photo-ionized by protostar shock ionization episodic
H2O masers: 100 km/sec proper motion rotation of molecular jet predicted by magneto- centrifugal jet theory Pudritz et al. 2005
Hofner et al. 2007
N1
NRAO Socorro 05/2009
G31.41+0.31
Outflow characteristics:
L ~ 20L, M > 15 M
Tdyn ~ 4 x 103 yr
CH3OH (44.1 GHz)
Distance: 7.9 kpc LIRAS: 2.6 x 105 L (06 ZAMS) NH3(4,4) Size: 2" – 0.08 pc n(H2) 107 cm-3
T= 200 K (CH3CN)
Cesaroni et al. , in prep. Araya et al. 2008
NRAO Socorro 05/2009
DR21(OH)
MM1: L= 1.7 x 104 L, B0.5V ZAMS, M ~ 350 M,T ~ 60 K
MM2: Early B ZAMS, M ~ 570 M, T ~ 30 K
Davis et al. 2007 Araya et al. 2009
NRAO Socorro 05/2009
Photoevaporating Accretion DisksHollenbach et al. 1994, Yorke et al. 1996, Lizano et al. 1996, Lugo et al. 2004,
Originally developedfor UCHII/HCHII regions
Diffuse Ionization Static ionized atmospherewithin gravitational radius rg
Photoevaporative flowfor r > rg
NRAO Socorro 05/2009
Orion Source I Reid et al. 2007
Orion KL Source Id=414 pc
VLA: SiO J=1-0, v=0, 1, 2 7mm continuum FWHM: 30 mas
Ionized accretion disk (+ Jet ?)
H2O
NRAO Socorro 05/2009
Other Candidates Gibb et al. 2007
CO FlowCO Flow
S140-IRS1 VLA 7mm S106-IR MERLIN 1.3cm
NRAO Socorro 05/2009
Accretion Shocks Neufeld et al. 1994, 1996
Supersonic Infall: vs = 5 – 100 km/secPre-Shock Densities: nH = 107.5 – 1012 cm-3
Ionized pre/post-shock layer cm/mm free-free emission
NRAO Socorro 05/2009
Accretion Shocks Neufeld et al. 1994, 1996
High optical depths High brightness temperatures
NRAO Socorro 05/2009
Accretion Shocks Neufeld et al. 1994, 1996
Assumptions: Cassen & Moosman 1981 Infall Solution Accretion Rate: 10-4 M/year Accretion Radius: 10 AU Central Mass: 10 M
Predicted fluxes: 1.2 Jy (X) dist. = 5 kpc (4 mas) 31 Jy (Q)
7.5 Jy (X) dist. = 2 kpc (10 mas) 200 Jy (Q)
NRAO Socorro 05/2009
IR Counterparts
Precise Positions of massive protostars: adaptive optics, w/ laser guide star: similar resolutionUnclear why detectable at NIR: massive dust condensations predict AV > 1000
IRAS18566: SPITZER/IRAC VLA-7mm/2MASS-K
Araya et al. 2007 Anderson et al. in prep.
NRAO Socorro 05/2009
X-Ray Counterparts
IRAS20126: CHANDRA VLA –A conf.
Anderson et al. , in prep.
0.5 – 8 keV 3.6 cm
NRAO Socorro 05/2009
EVLA
• Jy sensitivity across a wide range of wavelengths
• Observe entire sample of massive protostars • Map brightness distribution, SED
• Relative duration of different physical scenarios
• Correlate with other age indicators: Evolution
• However: want matching resolution: e-MERLIN