LARGE-SCALE SHOCKS IN THE GALACTIC CENTER AND OTHER REGIONS

scientific abstract molecular gas within a few hundred parsecs of the galactic center displays considerable noncircular motion, perhaps as a response of the gas to a central bar potential, or as a result of one or more violent releases of energy in the past. the tumult characterizing molecular cloud kinematics there is accompanied by strong shock interactions between clouds, or between clouds and the ambient medium. we propose to investigate, with 3.1 hours of iso time, two examples of largescale shocks in the galactic center region: afgl 5376 and g0.020.07. in case the galactic center is not visible, we propose instead to study the shock in b35 near the lambda orionis ring and to map the h2o distribution in the snr ic 443 for a total of 6 hr. afgl5376 is an unusually strong 25micron infrared source which coincides with a remarkable vertical shock rising almost 100 pc above the galactic plane at a projected distance of 75 pc from the galactic center. the shock is inferred from a sharp discontinuity in the anomalousvelocity co emission at this location. g0.020.07 is a series of compact hii regions aligned along the interface between the dense, massive 50 km/s molecular cloud and the sgr a east nonthermal radio source with which it is interacting. the stars in these hii regions may have formed as a result of cloud compression by a shock associated with the expansion of sgr a east, or as a result of the collision of two clouds. both systems provide an unprecedented opportunity to study shocks under very different conditions than encountered normally (large size, extreme velocities, large magnetic fields). since shocks radiate primarily in the infrared, iso will be uniquely qualified to study these regions and to assess existing shock models in terms of their predictions for line strengths. comparison with more standard.. shocks such as orion/kl and ic 443 should help establish the importance of the high v truncat [truncated!, Please see actual data for full text]