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PI Total time #CoIs, team

Disk dynamics in very young stellar objects: the contribution from ALMA

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PI Total time #CoIs, team

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  1. Disk dynamics in very young stellar objects: the contribution from ALMA Two formation scenarios exist for massive stars: non spherical accretion and merging of lower mass stars. Discriminating between these two models represents a challenging observational goal. The high sensitivity and spatial resolution of ALMA will shed light on this topic. • PI • Total time • #CoIs, team Silvia Leurini 24h (ALMA, extended and compact configurations, APEX?) Menten, Schilke, Stanke, Wyrowski

  2. How do massive stars form? • coalescence of stars (M<8M)? then we should detect high density of stars (108 pc-3) • accretion? then we should be able to observe accretion disks and collimated molecular outflows as in the case of low mass stars. A conclusive evidence of accretion from high mass stars is the detection of an outflow-disk system from a single protostar. Only a few disk candidates in massive stars are known, and all are early B type stars. No circumstellar disk has been detected in O type YSOs, but rotating structures, very massive (60-500 M) and extended (rd~4000-30000 AU), which are not in equilibrium.

  3. color: Spitzer 8m; red contours: N2H+ (cold molecular gas); black contours: CH3OH (warm molecular gas) Unambiguous probe of disks: Detection of continuum emission from a small (<0.1 pc) core located at the center of a bipolar outflow, AND of molecular emission with a velocity gradient PERPENDICULAR to the outflow. Potential molecular tracers of a disk are high-energy, optically thin lines of a low-abundance molecular species.

  4. ALMA Justification: high resolution, high sensitivity. Legacy Value: High statistics is needed. This will be part of a legacy project aimed at investigating circumstellar disks in high mass YSOs. Data Reduction: several lines will be observed simultaneously (large bandwidth correlator). There is a need for semi-automated tools for modelling the data, and better spectroscopic databases.

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