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 0.510 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.