1. 1)Are disks predicted?  Theories of HM SF 2)Are disks observed?  Search methods 3)Observational evidence  disks VS toroids 4)Open questions and the future: ALMA, etc. Search for Disks around Young High-Mass Stars Riccardo Cesaroni INAF-Osservatorio Astrofisico di Arcetri

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 disks of ~100-1000 AU See e.g. Bonnell 2005, Krumholz et al. 2007, Keto 2007, Kuiper et al. 2010  stars up to 137 M O 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. 50 AU molecular gas ionized gas density & velocity of gas around O9 star (Keto 2007)

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  need targets & tools Selection criteria for targets: Bolometric (IRAS) luminosity > several 10 3 L O  high-mass (proto)star Association with outflow  likely disk? Presence of massive (> 10 M O ), 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 H 2 O, CH 3 OH, 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 Jimenez-Serra et al. (2007,2009) PV plot along disk Keplerian rotation about 18 M O star thermal jet disk B field (23 mG) CH 3 OH masers Vlemmings et al. (2010) SO 2 600 AU 1000 AU

11. rel. Dec. [mas] NGC7538 IRS1 N Pestalozzi et al. (2004, 2009) model of Keplerian disk around 31 M O star CH 3 OH maser PV plot along disk disk plane

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

13. 4.5µm emission disk J23056+6016 Quanz et al. (2010) H K’ bipolar nebula 12 CO blue outflow lobe red & blue C 18 O disk

14. Major problems: Velocity gradient may be expansion instead of rotation Outflow multiplicity 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. IRAS 20126+4104 Cesaroni et al. Hofner et al. Sridharan et al. Moscadelli et al. Image: 2µm cont. --- OH maser H 2 O masers 1000 AU Keplerian rotation+infall: M * =10 M O Moscadelli et al. (2010) CH 3 OHH2OH2O 200 AU jet disk+jet disk

16. Distance measurement to IRAS 20126+4104 with H 2 O 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 13 CO -0.5” 0.5”1”0 NH 3 (1,1) CH 3 OH IRAS23151 NGC7538 IRAS20126 CepAHW2 CH 3 OH NGC7538S DCN C 17 O AFGL5142 AFGL490 IRAS18566 M17 W33A CO v=2-0

19. disk model 2.2µm VLT disk model2.2µm VLT model 2.2µm VLTI disk IR detected disks AFGL2591 2.1µm speckle 2.2µm Subaru J23056 IRAS20126 M17UC1 M17 19µm Subaru HD200775 IRAS13481 2.2µm UKIRT Kraus+ 2010 Quanz+ 2010 Sridharan+ 2005 Steinecker+ 2006 Nielbock+ 2007 Kraus+ 2010 Okamoto+ 2009

20. Velocity fields of rotating toroids C G24 A1 G24 A2 G31.41 G19.61 G10.62 G327 G351 G305 G28.20 CH 3 CN NH 3

21. Toroids M > 100 M O R ~ 10000 AU L > 10 5 L O  O (proto)stars small t acc /t rot  non-equilibrium, circum- cluster structures Disks M < a few 10 M O R ~ 1000 AU L ~ 10 4 L O  B (proto)stars large t acc /t rot  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. IRDC18223-3 Fallscheer et al. (2009) CH 3 OH 5000 AU disk model small-scale velocity field large-scale bipolar outflow disk-model velocity field 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. G31.41+0.31 Cesaroni et al. in prep. W51e2 Tang et al. (2009) Keto & Klaassen (2008) 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. tidal destruction rotational period photo-evaporation 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. Assumptions: HPBW = R disk /4 FWHM line = V rot (R disk ) M disk  M star same in all disks T B > 20 K obs. freq. = 230 GHz 5 hours ON-source spec. res. = 0.2 km/s S/N = 20 edge-on i = 35° circumstellar disks Keplerian

30. Assumptions: HPBW = R disk /4 FWHM line = V rot (R disk ) M disk  M star same in all disks T B > 20 K obs. freq. = 230 GHz 5 hours ON-source spec. res. = 0.2 km/s S/N = 20 no stars edge-on i = 35°

31. Simulations of disks around 8 M O star Krumholz et al. (2007) NH 3 with EVLA CH 3 CN(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. Furuya et al. (2008) CH 3 CN Sanna et al. (2010) rotating toroid deeply embedded disk? CH 3 OH masers 1.3cm cont.

35. IRAS18566+0408 Araya et al. (2007) (7mm cont., dust) (cm cont., free-free) maser SiO jet Zhang et al. (2007)

36. DR21(OH)N Harvey-Smith et al. (2008) Linear distribution of OH maser spots Keplerian pattern in PV plot

37. CepA HW2 Jimenez-Serra et al. (2007,2009) PV plot along disk Keplerian rotation about 18 M O star thermal jet disk H 2 O masers PV plot Torrelles et al. (1996) SO 2

38. IRAS 20126+4104 Cesaroni et al. Hofner et al. Moscadelli et al. Keplerian rotation: M * =7 M O Moscadelli et al. (2005)

39. outflow Theorist’s definition: Disk = long-lived, flat, rotating structure in centrifugal equilibrium Observer’s definition: Disk = elongated structure with velocity gradient perpendicular to outflow axis core disk What to search for?

40. CepA HW2 Jimenez-Serra et al. (2007,2009) PV plot along disk Keplerian rotation about 18 M O star thermal jet disk SO 2

41. Existence of disks: Observations Naïve paradigm: infall  disk + outflow Outflows are easy to observe i.Outflows equally common from solar-type to O-type stars (Beuther et al. 2002, Wu et al. 2004, Sepulcre et al. 2009) ii.Outflow parameters (e.g. momentum rate) vary smoothly from low- to high-mass stars iii.Disks do exist in low-mass stars i+ii+iii  Disks should exist also in high-mass stars! This is no proof, but very encouraging…

42. Observational results Evidence for rotation in ~42 molecular cores: ~26 disks  Keplerian rotation in ~10 of these ~16 rotating toroids  not Keplerian ~6 disks seen in the IR (absorption/emission) some (>2) studied in maser lines  absolute proper motions  3D velocities (+distance)

43. Observational results Evidence for rotation in ~42 molecular cores: ~26 disks  Keplerian rotation in ~10 of these ~16 rotating toroids  not Keplerian ~6 disks seen in the IR (absorption/emission) some (>2) studied in maser lines  absolute proper motions  3D velocities (+distance)