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Disks (and outflows) in high-mass YSOs

Disks (and outflows) in high-mass YSOs. in collaboration with : M.T. Beltràn, C. Codella, R. Furuya, P. Hofner, L. Moscadelli, R. Neri, L. Olmi, L. Testi, C.M. Walmsley and many more…. Importance of disks for high-mass star formation: accretion vs merging

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Disks (and outflows) in high-mass YSOs

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  1. Disks (and outflows) in high-mass YSOs in collaboration with: M.T. Beltràn, C. Codella, R. Furuya, P. Hofner, L. Moscadelli, R. Neri, L. Olmi, L. Testi, C.M. Walmsley and many more… • Importance of disks for high-mass star formation: accretion vs merging • Search for disks in massive YSOs: targets and tracers • Results: Keplerian and self-gravitating disks

  2. Disks and star formation Star formation contraction + conserv. of angul. momentum rotation and flattening: “disk” Observer’s definition: Disk = elongated and rotating structure • Keplerian disks found in low-mass YSOs • Disks in high-mass YSOs would be even more important…

  3. Low-mass vs High-mass • Lowmass (< 8 M): taccr < tcontr • Highmass (> 8 M): taccr > tcontr • High-mass stars “switch on” still accreting  radiation pressure stops accretion  stars > 8 M cannot form!? Solutions: • non-spherical accretion: disks (and outflows) • merging of stars < 8 M

  4. Search for disks in high-mass YSOs • Target:hot cores (<0.1 pc, 10-103 M, 100 K) with jet/outflow • Tracer:“rare” species: CH3CN, NH3, CH3OH •  Test: core with velocity gradientperpendicular to outflow axis: outflow outflow core

  5. Likely candidates for disks

  6. Gibb et al. 2002

  7. Gibb et al. 2002

  8. Gibb et al. 2002

  9. Gibb et al. 2002

  10. Gibb et al. 2002

  11. Gibb et al. 2002

  12. Higher angular resolution desirable: • ALMA down tofew mas, but only after 2010… • at present: 7mm cont. with VLA (40 mas)andmasers(H2O, OH, CH3OH)with VLBI (1 mas) • VLA/VLBI observations give ambiguous results for disks in massive YSOs…

  13. Conclusions • Disks in high-mass YSOs do exist: 10-1000 M, 100-1000 AU • Most disks in high-mass YSOs appear to be unstable Disks  formation by accretion plausible Accretion diskslong-lived entities

  14. Search for disks in high-mass YSOs • Target:hot cores (<0.1 pc, 10-103 M, 100 K) with jet/outflow • Tracer:“rare” species: CH3CN, NH3, CH3OH •  Test: core with velocity gradientperpendicular to outflow axis • Problems: • large distance (a few kpc): sub-arcsec resolution • inclination of disk axis: 90° good for disk, 0° good for outflow

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