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Search for Disks around Young High-Mass Stars

Search for Disks around Young High-Mass Stars. Riccardo Cesaroni INAF-Osservatorio Astrofisico di Arcetri. Are disks predicted ?  Theories of HM SF Are disks observed ?  Search methods Observational evidence  disks VS toroids Open questions and the future : ALMA , etc.

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Search for Disks around Young High-Mass Stars

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  1. Search for Disks around YoungHigh-Mass Stars Riccardo Cesaroni INAF-Osservatorio Astrofisico di Arcetri • Are disks predicted?  Theories of HM SF • Are disks observed?  Search methods • Observational evidence  disks VS toroids • Open questions and the future: ALMA, etc.

  2. Existence of disks: Theory Disks are natural outcome of infall + angular momentum conservation, however: • B field  magnetic braking, pseudo disks? • Ionization by OB stars  photoevaporation? • Tidal interaction with cluster  truncation? • Merging of low-mass stars  destruction?  Disks in OB protostars might not exist!

  3. Good news: all theories predict circumstellar disks! Different models of high-mass star formation (core accretion, competitive accretion, …), but all predict circumstellar disksof ~100-1000 AU See e.g. Bonnell 2005, Krumholz et al. 2007, Keto 2007, Kuiper et al. 2010  stars up to 137 MO through disk accretion

  4. 1 pc clump collapse competitive accretion Bonnell (2005)

  5. Zoom in time core accretion in 0.2 pc clump Krumholz et al. (2007) disk

  6. density & velocity of gas around O9 star (Keto 2007) ionized gas molecular gas 50 AU

  7. Bad news:all theories predict circumstellar disks! Disks existence not sufficient to choose SF theory Disks may keep memory of formation process disks properties needed to discriminate between SF models • < 100 AU resolution necessary, i.e. < 0.1” • ALMA, EVLA, eMERLIN, VLBI, VLTI, …

  8. The search for disks Many searches in the last decade  needtargets & tools Selection criteria for targets: • Bolometric (IRAS) luminosity > several 103 LO high-mass (proto)star • Association with outflow  likely disk? • Presence of massive (> 10 MO), compact (< 0.1 pc) molecular core  deeply embedded (young) high-mass object • In some cases maser and/or UCHII  OB stars

  9. Tools adopted: • Thermal lines of rare (low-abundance) molecules  trace high-density, high-temperature gas in disk • H2O, CH3OH, OH, SiO maser lines  mas resolution • (sub)mm continuum  disk mass • IR continuum/lines  disk emission and absorption • cm continuum and RRL  ionised accretion flow Diagnostic: • Flattened (sub)mm core perpendicular to jet/outflow • Velocity gradient perpendicular to associated outflow • Peculiar (Keplerian) pattern in position-velocity plot • Dark silouhette in near-IR against bright background • Elongated emission in the mid-IR perpendicular to bipolar reflection nebula

  10. CepA HW2 disk Jimenez-Serra et al. (2007,2009) PV plot along disk 1000 AU SO2 Keplerian rotation about 18 MO star 600 AU B field (23 mG) CH3OH masers Vlemmings et al. (2010) thermal jet

  11. NGC7538 IRS1 N Pestalozzi et al. (2004, 2009) model of Keplerian disk around 31 MO star PV plot along disk CH3OH maser rel. Dec. [mas] disk plane

  12. Nuerberger et al. (2007) M17 Chini et al. (2004) disk H2 jet 2.2 µm continuum 2 µm lines

  13. J23056+6016 Quanz et al. (2010) 12CO blue outflow lobe 4.5µm emission disk H K’ bipolar nebula red & blue C18O disk

  14. Major problems: • Velocity gradient may be expansion instead of rotation • Outflowmultiplicity and/or precession • Masers sample only few lines of sight • (sub)mm & IR continuum: no kinematical info • IR lines: so far limited spectral resolution Possible solutions: • High angular & spectral resolution  accurate PV plots  Keplerian rotation (close enough to star) • Maser proper motions  3D velocity  Combine as many tools as possible!

  15. Keplerian rotation+infall: M*=10 MO Image: 2µm cont. --- OH maser H2O masers Moscadelli et al. (2010) disk+jet disk 1000 AU jet 200 AU CH3OH H2O IRAS 20126+4104 Cesaroni et al. Hofner et al. Sridharan et al. Moscadelli et al.

  16. Distance measurement to IRAS 20126+4104 with H2O maser parallax (Moscadelli et al. 2010) d = 1.64±0.05 kpc

  17. Observational results • Evidence for rotation/flattening in ~42 molecular cores: ~26 disks  Keplerian rotation in ~10 of these ~16 rotating toroids  velocity gradient perpendicular to outflow/jet, but not Keplerian

  18. PV plots of candidate Keplerian disks in high-mass stars W33A M17 13CO CO v=2-0 NGC7538S IRAS23151 CH3OH CepAHW2 IRAS18566 DCN C17O NGC7538 AFGL5142 CH3OH IRAS20126 AFGL490 NH3(1,1) -0.5” 1” 0.5” 0

  19. Steinecker+ 2006 model 2.2µm VLT IR detected disks M17UC1 Nielbock+ 2007 disk M17 J23056 IRAS20126 disk Sridharan+ 2005 2.2µm VLT model disk HD200775 Kraus+ 2010 AFGL2591 19µm Subaru disk Quanz+ 2010 2.2µm UKIRT 2.2µm Subaru disk Kraus+ 2010 model 2.2µm VLTI Okamoto+ 2009 2.1µm speckle IRAS13481

  20. Velocity fields of rotating toroids G24 A1 G24 A2 G305 G327 C G31.41 CH3CN G351 G10.62 G19.61 CH3CN G28.20 NH3 NH3 CH3CN

  21. Toroids M > 100 MO R ~ 10000 AU L > 105 LO O (proto)stars small tacc/trot non-equilibrium, circum-cluster structures Disks M < a few 10 MO R ~ 1000 AU L ~ 104 LO B (proto)stars large tacc/trot equilibrium, circumstellar structures disks toroids Beltran et al. (2010)

  22. Open questions • When do disks appear? 1 disk/toroid in IR-dark cloud • Role of magnetic field? 2 toroids with B parallel to rotation axis  B may play crucial role • Why no (Keplerian) disks seen in O stars? • Ionized by OB stars? Unlikely: too slow and rotation in ionized gas detected in G10.62 (Keto & Wood 2005) • Truncated by tidal interactions in cluster? Maybe, but numerical simulations needed • Too far? ALMA and EVLA should tell us! • Too deeply embedded in toroids? Optically thin (low abundance i.e. high density) tracers needed, but line forest may fool even ALMA!  VLBI of masers may help

  23. disk model CH3OH 5000 AU IRDC18223-3 Fallscheer et al. (2009) disk-model velocity field small-scale velocity field large-scale bipolar outflow 0.2 pc

  24. Open questions • When do disks appear? 1 disk/toroid in IR-dark cloud • Role of magnetic field? 2 toroids with B parallel to rotation axis B may play crucial role • Why no (Keplerian) disks seen in O stars? • Ionized by OB stars? Unlikely: too slow and rotation in ionized gas detected in G10.62 (Keto & Wood 2005) • Truncated by tidal interactions in cluster? Maybe, but numerical simulations needed • Too far? ALMA and EVLA should tell us! • Too deeply embedded in toroids? Optically thin (low abundance i.e. high density) tracers needed, but line forest may fool even ALMA!  VLBI of masers may help

  25. Keto & Klaassen (2008) Cesaroni et al. in prep. G31.41+0.31 W51e2 Tang et al. (2009) Girart et al. (2009)

  26. Open questions • When do disks appear? 1 disk/toroid in IR-dark cloud • Role of magnetic field? 2 toroids with B parallel to rotation axis  B may play crucial role • Why no (Keplerian) disks seen in O stars? • Ionized by OB stars? Unlikely: too slow and rotation in ionized gas detected in G10.62 (Keto & Wood 2005) • Truncated by tidal interactions in cluster? Maybe, but numerical simulations needed • Too far? ALMA and EVLA should tell us! • Too deeply embedded in toroids? Optically thin (low abundance i.e. high density) tracers needed, but line forest may fool even ALMA!  VLBI of masers may help

  27. photo-evaporation tidal destruction rotational period Cesaroni et al. (2007)

  28. Open questions • When do disks appear? 1 disk/toroid in IR-dark cloud • Role of magnetic field? 2 toroids with B parallel to rotation axis  B may play crucial role • Why no (Keplerian) disks seen in O stars? • Ionized by OB stars? Unlikely: too slow and rotation in ionized gas detected in G10.62 (Keto & Wood 2005) • Truncated by tidal interactions in cluster? Maybe, but numerical simulations needed • Too far? ALMA and EVLA should tell us! • Too deeply embedded in toroids? Optically thin (low abundance i.e. high density) tracers needed, but line forest may fool even ALMA!  VLBI of masers may help

  29. circumstellar disks Assumptions: HPBW = Rdisk/4 FWHMline = Vrot(Rdisk) Mdisk Mstar same <Ncol> in all disks TB > 20 K obs. freq. = 230 GHz 5 hours ON-source spec. res. = 0.2 km/s S/N = 20 edge-on i = 35° Keplerian

  30. Assumptions: HPBW = Rdisk/4 FWHMline = Vrot(Rdisk) Mdisk Mstar same <Ncol> in all disks TB > 20 K obs. freq. = 230 GHz 5 hours ON-source spec. res. = 0.2 km/s S/N = 20 edge-on i = 35° no stars

  31. Simulations of disks around 8 MO star Krumholz et al. (2007) NH3 with EVLA CH3CN(12-11) with ALMA cont. + line cont. subtr.

  32. Open questions • When do disks appear? 1 disk/toroid in IR-dark cloud • Role of magnetic field? 2 toroids with B parallel to rotation axis  B may play crucial role • Why no (Keplerian) disks seen in O stars? • Ionized by OB stars? Unlikely: too slow and rotation in ionized gas detected in G10.62 (Keto & Wood 2005) • Truncated by tidal interactions in cluster? Maybe, but numerical simulations needed • Too far? ALMA and EVLA should tell us! • Too deeply embedded in toroids? Optically thin (low abundance i.e. high density) tracers needed, but line forest may fool even ALMA!  VLBI of masers may help

  33. CH3CN deeply embedded disk? rotating toroid CH3OH masers 1.3cm cont. Furuya et al. (2008) Sanna et al. (2010)

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