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Session 53 - Circumstellar Disks & Outflows Associated with YSOs.
Oral session, Tuesday, January 14
Piers 4/5,
Bipolar outflows from young stars impact the surrounding molecular cloud core through shock heating, turbulence, and shearing. Energy is transported across large distances, affecting the character of future star formation. Some models of outflow structure include an ionized inner region, with lower velocity and less collimated neutral gas making up the outflow further from the central source. However, the exact nature of the structure and effects of outflows have been difficult to observationally confirm until recently because of instrumental sensitivity and resolution limitations.
Here we present new VLA detections of both the structure and the large scale effects of outflows in two regions of high mass star formation. One such source, DR 21, contains at least one vigorous bipolar outflow. Recent single-dish observations revealed evidence for very high velocity ionized gas in the region, with line wings of recombination line spectra extending several hundreds of kilometers per second from the central line peak. We have mapped this ionized gas with the VLA, revealing the spatial relationship of the high velocity ionized gas with the bipolar lobes of the previously detected molecular outflow in the region. High spectral dynamic range imaging techniques allow the possibility of detecting an inner ionized high velocity component within this powerful outflow.
We also present a high resolution mosaic of high velocity heated gas in the Orion OMC-1 outflow region. Emission from the ammonia (3,3) inversion transition was observed, which is sensitive to gas heated within the outflow or in regions heated as the outflow shocks and shears the surrounding filamentary molecular gas environment. Several fields were combined to create a linear mosaic covering a 3' x 3' region. We present maps which reveal dense molecular gas blueshifted to high velocities from a central region near the "hot core". Temperatures derived from the region show a direct relation between the spatial paths where the outflow lobes escape from the central core, and "hot spots" where the heated gas shears past the surroundings. These results show dynamic and far reaching effects of outflows on their environment.
