Shock-Wave Model of the Kinematic Features of Neutral Hydrogen and Molecules CO, OH, and H,CO near the Galactic Center
A method of calculating the propagation and structure of a shock wave is proposed for the shock wave originating impulsively at the galactic nucleus and propagating outward through the interstellar medium. The propagation of the shock front little differs among the various, but probably acceptable, states of the unperturbed nuclear disk, while the width of high-density region behind the front broadens with magnetic strength. The negative high-velocity features observed at the longitude range o. 1.7o in molecules CO, OH, and H2CO and in neutral hydrogen are consistently interpreted to be due to the expanding shock wave whose front is propagating at 290 pc from the center on the near side of the center; the hydrogen with the highest velocity corresponds to the gas just behind the shock front and the molecules with the relatively slower velocity stratify in the layer of 20 pc slightly behind the front. Contracting gas far behind the shock front seems to form highly condensed regions around 100-150 pc of the center. The shock wave originated 1 x 106 yr ago and its expansion velocity was 1200km 1 at 20 pc. The origin of the asymmetric propagation of the shock wave is discussed. Key words: Galactic center region; Gaseous kinematics; Shock wave.
Publications of the Astronomical Society of Japan
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