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Radio Continuum Studies of Massive Protostars

Radio Continuum Studies of Massive Protostars. Peter Hofner New Mexico Tech & NRAO. Collaborators. E. Araya NRAO/UNM S. Kurtz, L. Rodriguez CRyA-UNAM M. Goss, D. Shepherd NRAO

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Radio Continuum Studies of Massive Protostars

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  1. Radio Continuum Studies of Massive Protostars Peter Hofner New Mexico Tech & NRAO

  2. 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

  3. Outline • Introduction: DR21 • VLA Observations of Massive Protostars: • Jets • Photoevaporating Disks • Accretion Shocks • IR and X-Ray Counterparts

  4. 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

  5. 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

  6. Compact HII Region Ryle & Downes 1967: Cambridge 1 mile Interferometer: First Aperture Synthesis, 1.4 GHz, FWHM: 30" DR21: the first compact HII region

  7. Ultracompact HII Regions Harris 1973 Cambridge 5 km Interferometer 5 GHz, FWHM: 3" Component D: Cometary UCHII Region EM= 8.2x107 pc cm-6, ne=6.5x104 cm-3 Central star: B0

  8. 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, 2000 Sridharan et al. 2002, Beuther et al. 2002

  9. 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

  10. 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   

  11. 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

  12. + 44 GHz CH3OH Masers + + + + + Cesaroni et al. 1999 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 ?

  13. Hofner et al. 2007 IRAS 20126+4104 • VLA A-configuration X-band • Where is the massive protostar ? • a) In between N1 and N2 • b) Near peak of N1 • c) Somewhere else

  14. Hofneret al. 2007 IRAS 20126+4104 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)

  15. 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 N1  Hofneret al. 2007

  16. G31.41+0.31 Cesaroni et al. , in prep. Araya et al. 2008 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) Outflow characteristics: L ~ 20L, M > 15 M Tdyn ~ 4 x 103 yr

  17. DR21(OH) Araya et al. 2009 Davis et al. 2007 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

  18. Photoevaporating Accretion Disks Hollenbach et al. 1994, Yorke et al. 1996, Lizano et al. 1996, Lugo et al. 2004, Originally developed for UCHII/HCHII regions Diffuse Ionization  Static ionized atmosphere within gravitational radius rg Photoevaporative flow for r > rg

  19. Orion Source I Reid et al. 2007 Orion KL Source I d=414 pc VLA: SiO J=1-0, v=0, 1, 2 7mm continuum FWHM: 30 mas Ionized accretion disk (+ Jet ?) H2O

  20. Other Candidates Gibb et al. 2007 S140-IRS1 VLA 7mm S106-IR MERLIN 1.3cm CO Flow CO Flow

  21. Accretion Shocks Neufeld et al. 1994, 1996 Supersonic Infall: vs = 5 – 100 km/sec Pre-Shock Densities: nH = 107.5 – 1012 cm-3  Ionized pre/post-shock layer  cm/mm free-free emission

  22. Accretion Shocks Neufeld et al. 1994, 1996 • High optical depths • High brightness temperatures

  23. 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)

  24. IR Counterparts IRAS18566: SPITZER/IRAC VLA-7mm/2MASS-K Anderson et al. in prep. Araya et al. 2007 Precise Positions of massive protostars: adaptive optics, w/ laser guide star: similar resolution Unclear why detectable at NIR: massive dust condensations predict AV>1000

  25. X-Ray Counterparts IRAS20126: CHANDRA VLA –A conf. 0.5 – 8 keV 3.6 cm Anderson et al. , in prep.

  26. 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

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