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Outflow, infall, and rotation in high-mass star forming regions

Outflow, infall, and rotation in high-mass star forming regions. Riccardo Cesaroni Osservatorio Astrofisico di Arcetri. High-mass vs low-mass: the dividing line The formation of high-mass stars: accretion vs coalescence Observations: infall , outflows , and disks

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Outflow, infall, and rotation in high-mass star forming regions

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  1. Outflow, infall, and rotation in high-mass star forming regions Riccardo Cesaroni Osservatorio Astrofisico di Arcetri • High-mass vs low-mass: the dividing line • The formation of high-mass stars: accretion vs coalescence • Observations: infall, outflows, and disks • Kinematical evidence supports accretion

  2. Low-mass vs High-mass Theory (Shu et al. 1987): star formation from inside-out collapse onto protostar Two relevant timescales: accretion  tacc = M*/(dM/dt) contraction  tKH = GM*/R*L* • Lowmass (< 8 MO): tacc < tKH • Highmass (> 8 MO): tacc > tKH  accretion onZAMS

  3. PROBLEM: High-mass stars “switch on” still accreting  radiation pressure stops accretion   stars > 8 MOcannot form!? SOLUTIONS Yorke (2003): Kdust<Kcrit M*/L* • “Reduce’’ L*: non-spherical accretion • “Increase’’ M*: large accretion rates • Reduce Kdust: large grains (coalescence of lower mass stars)

  4. Possible models • (Non-spherical) accretion: Behrend & Maeder (2001); Yorke & Sonnhalter (2002); Tan & McKee (2003) ram pressure > radiation pressure • Coalescence: Bonnell et al. (2004) many low-mass stars merge into one massive star

  5. Implications & predictions • Accretion • infalldisksoutflows • isolated star formation possible • massive stars form at cluster centre: (dM/dt)  FWHM3(Shu et al. 1987) • massive stars form with lower mass stars: t  M*1/4(Tan & Mc Kee 2003)

  6. Implications & predictions • Coalescence • infall, low-mass disks, multiple outflows • isolated star formation impossible • massive stars form at cluster centre: large n*(108 */pc3 !) many collisions • massive stars form after lower mass stars

  7. best discriminant between models: kinematics of molecular gas • infall: accretion  large accretion rate coalescence  small(?) accretion rate • outflow: accretion  single massive flow coalescence  multiple low-mass flows • rotation: infall+ang. mom. conservation   rotating disks (“only’’ in accretion model)

  8. best discriminant between models: kinematics of molecular gas • infall: accretion  large accretion rate coalescence  small(?) accretion rate • outflow: accretion  single massive flow coalescence  multiple low-mass flows • rotation: infall+ang. mom. conservation   rotating disks (“only’’ in accretion model)

  9. best discriminant between models: kinematics of molecular gas • infall: accretion  large accretion rate coalescence  small(?) accretion rate • outflow: accretion  single massive flow coalescence  multiple low-mass flows • rotation: infall+ang. mom. conservation   rotating disks (“only’’ in accretion model)

  10. best discriminant between models: kinematics of molecular gas • infall: accretion  large accretion rate coalescence  small(?) accretion rate • outflow: accretion  single massive flow coalescence  multiple low-mass flows • rotation: infall+ang. mom. conservation   rotatingdisks (“only’’ in accretion model)

  11. Discriminating between models: observations • Observational problems: • IMF  high-mass stars are rare • formation in clusters  confusion • rapidevolution: tacc=20 MO /10-3MOyr-1=2104yr • large distance: >300 pc, typically a few kpc • parental environment profoundly altered • Advantage: • very luminous (cont. & line) and rich (molecules)!

  12. High-mass star forming region 0.5 pc

  13. G9.62+0.19 NIR J+H+K 10 pc

  14. G9.62+0.19 350 micron 0.5 pc Hunter et al. (2000)

  15. Testi et al. Cesaroni et al.

  16. Infall Difficult to reveal: Vff  R-0.5 • direct evidence: • red-shifted (self)absorption: ambiguous… • position-velocity plots/channel maps • indirect evidence: • lack of support: Mgas > Mvir • model fit to SED • dM/dt=10-3—10-2MOyr-1 accretion possible • insufficient resolution: infall on single star?

  17. Infall • Difficult to reveal: Vff  R-0.5 • direct evidence: • red-shifted (self)absorption: ambiguous… • position-velocity plots/channel maps • indirect evidence: • lack of support: Mgas > Mvir • model fit to SED • dM/dt=10-3—10-2MOyr-1 accretion possible • insufficient resolution: infall on single star?

  18. Infall • Difficult to reveal: Vff  R-0.5 • direct evidence: • red-shifted (self)absorption: ambiguous… • position-velocity plots/channel maps • indirect evidence: • lack of support: Mgas > Mvir • model fit to SED • dM/dt=10-3—10-2MOyr-1 accretion possible • insufficient resolution: infall on single star?

  19. Outflow Easy to detect even with low angular resolution • single-dish (>10” i.e. >0.5 pc) CO surveys of UCHIIs, IRAS sources, masers (Shepherd & Churchwell 1996; Zhang et al. 2001; Beuther et al. 2002, etc.), H2 (shocked) 2.2m emission • outflows in high-mass stars do exist • typical parameters: 1 pc, 5—5000 MO, 10-4—10-2MO yr-1, dM/dt  L0.7 BUT… are these from the most massive (proto)star?

  20. CO(2-1) outflow & 1mm continuum Beuther et al. (2002)

  21. Outflow • Easy to detect even with low angular resolution • single-dish (>10” i.e. >0.5 pc) CO surveys of UCHIIs, IRAS sources, masers (Shepherd & Churchwell 1996; Zhang et al. 2001; Beuther et al. 2002, etc.), H2 (shocked) 2.2m emission • outflows in high-mass stars do exist • typical parms.: 1 pc, 5-5000 MO,10-4-10-2MO yr-1 • dM/dt  L0.7 continuity from low- to high-mass BUT… is outflow from one massive (proto)star?

  22. CO outflows in YSOs Churchwell (2002) dM/dt  L0.7

  23. Outflow • Easy to detect even with low angular resolution • single-dish (>10” i.e. >0.5 pc) CO surveys of UCHIIs, IRAS sources, masers (Shepherd & Churchwell 1996; Zhang et al. 2001; Beuther et al. 2002, etc.), H2 (shocked) 2.2m emission • outflows in high-mass stars do exist • typical parms.: 1 pc, 5-5000 MO,10-4-10-2MO yr-1 • dM/dt  L0.7 continuity from low- to high-mass BUT… is outflow from one massive (proto)star?

  24. interferometric (>1” i.e. 0.05 pc) observations of selected targets in CO, HCO+, SiO, etc. (PdBI, OVRO, BIMA, NMA) • “single-dish’’ outflows resolved into (massive & collimated) multiple outflows (Beuther et al. 2002) • precession of outflow complicate interpretation (Shepherd et al. 2000; Gibb et al. 2003) • powering source difficult to identify  infall/outflow insufficient to prove model

  25. CO(2-1) & mm cont. Beuther et al. (2002) single-dish (12’’ beam)

  26. 05358+3543 Beuther et al. (2003) interferometer (4’’ beam)

  27. interferometric (>1” i.e. 0.05 pc) observations of selected targets in CO, HCO+, SiO, etc. (PdBI, OVRO, BIMA, NMA) • “single-dish’’ outflows resolved into (massive & collimated) multiple outflows (Beuther et al. 2002) • precession of outflow complicate interpretation (Shepherd et al. 2000; Gibb et al. 2003) • powering source difficult to identify  infall/outflow insufficient to prove model

  28. IRAS 20126+4104 Shepherd et al. (2000) blue lobe red lobe H2 knots

  29. IRAS 20126+4104 jet in H2 line

  30. IRAS 20126+4104 Cesaroni et al. (in prep.)

  31. interferometric (>1” i.e. 0.05 pc) observations of selected targets in CO, HCO+, SiO, etc. (PdBI, OVRO, BIMA, NMA) • “single-dish’’ outflows resolved into (massive & collimated) multiple outflows (Beuther et al. 2002) • precession of outflow complicate interpretation (Shepherd et al. 2000; Gibb et al. 2003) • powering source difficult to identify infall/outflow insufficient to prove scenario

  32. Disks Circumstellar accretion disks predicted only by accretion model! Any evidence? • Large scale (1 pc) rotating clumps seen in medium density tracers e.g. NH3 in G35.2-0.74 (Little et al. 1985) • Small scale (<0.1 pc) many claims of rotating “disks’’…

  33. Disks • Circumstellar accretion disks predicted only by accretion model! Any evidence? • Large scale (1 pc) • rotating clumps seen in medium density tracers e.g. NH3 in G35.2-0.74 (Little et al. 1985) • Small scale (<0.1 pc) • many claims of rotating “disks’’…

  34. CH3OH masers: stellar mass too low; H2 jets parallel to CH3OH spots (De Buizer 2003) • SiO & H2O masers: outflow or disk ? • NIR-cm cont.: confusion between disk and wind emission • Molecular lines: kinematical signature of disk & outflow

  35. CH3OH masers W48 Minier et al. (2000) M*=6 MO

  36. H2O masers Cep A HW2 Torrelles et al. (1996)

  37. CH3OH masers: stellar mass too low; H2 jets parallel to CH3OH spots (De Buizer 2003) • SiO & H2O masers: outflow or disk? • NIR-cm cont.: confusion between disk and wind emission? • Molecular lines: kinematical signature of disk &outflow core disk outflow outflow

  38. G192.16-3.82 Shepherd & Kurtz (1999) 2.6mm cont. disk CO outflow

  39. G192.16-3.82 Shepherd & Kurtz (1999) 3.6cm cont. & H2O masers

  40. NGC7538S Sandell et al. (2003)

  41. IRAS 20126+4104 Cesaroni et al.; Moscadelli et al. M*=7 MO H2O masers prop. motions

  42. Disks & Tori B stars O stars

  43. Gibb et al. (2002) Olmi et al. (2003) Beltran et al. (2004)

  44. Beltran et al. (2004)

  45. Beltran et al. (2004)

  46. Gibb et al. (2002) Olmi et al. (2003)

  47. Beltran et al. (2004) 1200 AU Hofner priv comm.

  48. Disks &Tori B stars O stars

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