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Chasing disks around massive stars with Malcolm

Chasing disks around massive stars with Malcolm. Disks and the formation of OB stars How HMCs studies turned into quest for disks Before ALMA: disks versus toroids The ALMA era: disks around B stars The current & future challenge : disks around O stars.

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Chasing disks around massive stars with Malcolm

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  1. Chasing disks around massive stars with Malcolm • Disks and the formation of OB stars • How HMCsstudiesturnedintoquest for disks • Before ALMA: disks versus toroids • The ALMA era: disks around B stars • The current & future challenge: disks around O stars

  2. «First things first!»(Malcolm priv. comm.): Why are disks so important? Star formation: inside-out collapseontoprotostar Tworelevanttimescales: accretiontacc= M*/(dM/dt) contractiontKH= GM*/R*L* • Lowmass (< 8 MO): tacc< tKH • Highmass (> 8 MO): tacc> tKHaccretion on ZAMS radiation pressure mayhaltaccretionin sphericalsymmetrydisk may be solution!

  3. Theory 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, 2011 stars up to 140 MO may form by disk accretion

  4. Existence of disks 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 protostarscould not exist!

  5. A little bit of history In the ’90s: • Growingevidenceof disks aroundlow mass YSOsfrom HST (proplyds; O’Dell et al. 1993) and mm interferometry (GG Tau, etc.; Dutrey et al. 1994, Simon et al. 2000) • Verylittleevidenceof disks aroundOB stars(G10.6-0.4; Keto et al. 1987, 1988): tooembedded, too far? Butmanystudies of hot molecularcores! (seeFriedrich’s talk)

  6. My collaboration with Malcolm: From HMCs to disks • HMCs are dense, hot, chemicallyrich: cradles of OB stars? • Surveys of UC HIIs, H2O masers, luminous IRAS sources, etc. to identifyHMCs • Tracers: NH3(4,4), CH3CN • Instruments: single-dish (IRAM, Effelsberg) interferometry (IRAM, VLA) of selectedobjects

  7. The special case of the G31.41+0.31 HMC (106 LO O type) UCHII HMC

  8. strong CH3CN(6-5) emission TB (K) frequency (GHz)

  9. Elongated distribution of velocity peaks with velocity gradient! Rotation or outflow? Rotation  Mdyn = 900 MO~ Mcore 2’’ resolution

  10. Velocity gradients found also in other luminous (O-type) HMCs, but too far  limited angular resolution & sensitivity closer HMCs needed B-type YSOs • Selected HMC: IRAS20126+4104 • distance 1.6 kpc  good spatial resolution • luminosity 104 LO massive enough • H2O masers  young and active • bipolar outflow  disk? • IRAM PdBI observations: • outflow tracer (HCO+) • High-density, high-temperature tracer (CH3CN) • 3 arcsec resolution

  11. outflow axis PdBI in 1995: CH3CN(6-5) 3’’ resolution Plots of peak positions in differentvelocitychannels: • elongatedperp. to outflow • velocitygradient

  12. jet disk PdBI in 1997: CH3CN(12-11) 0.7’’ resolution

  13. Malcolm’s insight: Keplerian rotation  FWHMΘS-0.5

  14. Image: H2 at 2µm CH3CN H2O masers IRAS 20126+4104 Cesaroni et al. (1997, 1999, 2005, 2013, 2014) Hofner et al. (1999, 2007) Moscadelli et al. (2005, 2010) Kepler+infall 8 MO star

  15. The search for disks After year 2000, several groups engaged in search for disks around massive stars. 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

  16. 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

  17. Our choice: molecular lines kinematical signature of rotation & outflow core disk outflow outflow

  18. Disks • M < a few 10 MO • R ~ 1000 AU L ~ 104 LOB (proto)stars • large tacc/trot circumstellarequilibrium structures Toroids • M > 100 MO • R ~ 10000 AU L > 105 LOO (proto)stars • small tacc/trot transientcircum-cluster structures Beltrán & de Wit (2017) Beltrán et al. (2010, 2014) Sánchez-Monge et al. (2014)

  19. Chasing disks with Malcolmin the ALMA era • Is the Keplerian disk around the B-type protostar IRAS20126+4104 unique?  ALMA Cycle 0: 0.4’’ observations of 2 YSOs at ~2 kpc, with 104 LO • Are there disks around O-type YSOs?  ALMA Cycle 2: 0.2’’ observations of 6 YSOs with >105 LO

  20. Typical ALMA spectra 13CH3CN CH3CN

  21. B-type YSOs

  22. Keplerian rotation about 18 MO G35.20-0.74 N Sanchez-Monge et al. (2013, 2014) ALMA350 GHz continuuum: • filament (~ 40 MO)perpendicolar to bipolar nebula • ~6 coresalong filament

  23. G35.03+0.35 • Prominent core (~4 MO) at center of bipolar nebula • Position-velocity plots along cut perpendicular to bipolar nebula • White pattern: Keplerian rotation about about 6 MO Beltrán et al. (2014)

  24. O-type YSOs

  25. 97 K 778 K K=2 v8=1 G31.41+0.31 CH3CN(1211) Beltrán et al. (2018) 10 times better resolution than first observation in 1994! high V + small offset  small R + high T  rotation Vrot ~ R-a

  26. AFGL4176 time Detectionrate depends more on L/Mthan on distanceage effect? • Too young disk too embedded: difficult detection • Tooold too few molecular gas

  27. Current situation: Up do date review on disks around massive stars (Beltrán & de Wit 2017): 41 disks/toroids around OB-type stars Red: OB stars Blue: int. mass stars

  28. Last paper with Malcolm (disk accretion and ejection): Radio follow-up of IR burst (Caratti o Garatti et al. 2017)

  29. S255 NIRS3 disk from C34S Zinchenko et al. (2015) Keplerian PV plot map burst!

  30. Conclusion • OK… disks, toroids, jets, bursts, etc., • all these may be very exciting, but… be scheptical and always keep in mind Malcolm’s warning:

  31. Io credo nulla! (I believe nothing!)

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