Infall, Rotation and Outflow in Four Massive Star Forming Regions
Pamela D. Klaassen
McMaster University, Hamilton, Canada
With high resolution observations of the gas surrounding massive star forming regions, we can can clearly determine which source (i.e. HII region instead of surrounding hot cores) are responsible for which dynamical structures (i.e. outflow, infall and rotation). The large distances to, and inherently clustered nature of massive star formation make it impossible to link specific dynamical structures to individual HII regions with single dish instruments alone.|
Here, we present ~1`` resolution observations of four well known massive star forming regions (G10.6, G28.20, NGC 7538 IRS1 and W51e2) obtained at the SMA (with supplementary JCMT observations incorporated when necessary). In a single tuning we show evidence for infall (in 13CO), rotation (in SO2) and large scale outflow (in 12CO) towards each source. When the optical depth is low enough, we have detected molecular infall signatures towards three sources (in either emission or absorption), while the fourth source was previously shown to have a molecular infall signature. We interpret the velocity gradients in the hot gas (as traced by SO2) surrounding each HII region as due to rotation since it is consistently perpendicular to the direction of the outflows observed in CO. Thus, we conclude that even for some of the most massive O stars, there is an active accretion phase beyond the formation of an HII region. This suggests support for the single accretion event scenario (i.e. McKee & Tan 2003) rather than the competitive accretion scenario.