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Session 121 - Molecular Clouds/Star Formation.
Oral session, Saturday, January 10
Georgetown,
Regions of high-mass star formation are considerably more complicated than their low-mass counterparts. Recent HST NICMOS images of Orion-KL (Thompson \itet al. 1997) as well as sensitive ground-based infrared images of H_2 shock emission in the Orion outflow region (Chrysostomou \itet al. 1997, McCaughrean amp; Mac Low 1997, Schild \itet al. 1997) reveal intricate clumpy shock structures extending in nearly all radial directions from the source. The one radial direction in which the shock emission is particularly diminished is to the northeast, and it is precisely here that a molecular gas filament is present and highly heated, as though blocking the path of outflowing material from Orion-KL.
We present our latest NH_3 (1,1), (2,2), and (3,3) VLA MEM mosaics of the Orion-KL region. We present evidence from temperature and chemical excitation gradients that the molecular gas cores along the filament extending to the northeast of Orion-KL are strongly heated by impacts from protostellar ejecta. These effects are seen in the core ``CS1'' 30'' northeast of IRc2 and also in cores at least twice as distant (1.5 pc).
The DR 21 outflow region is also quite complex, with multiple molecular outflows extending from a multiple-component HII region. We present sensitive VLA maps of hydrogen recombination line emission, and we report the detection of bipolar ionized gas within the molecular outflow lobes. This detection gives observational evidence for the initial ionized inner structure of high mass protostellar outflows.
Chrysostomou, A. \itet al. 1997, MNRAS, 289, 605
McCaughrean, M., amp; Mac Low, M.-M. 1997, AJ, 113, 391
Schild, H., Miller, S., amp; Tennyson, J. 1997, Aamp;A, 319, 1037
Thompson, R., Rieke, M., Schneider, G., Stolovy, S., Erickson, E., amp; Axon, D. 1997, STSCI Early Release Observation PRC97-13
