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Neutral hydrogen in the Galaxy and the galactic shocks


To discriminate the galactic shock theory from the linear density-wave theory in comparison with neutral hydrogen data in our Galaxy, we calculate model-line profiles andT b (l, v) (brightness temperature) diagrams of 21-cm line both for the two theories in the longitude range 15°≤l≤100°. It is shown that major differences between the two models appear in the tangential directions of spiral arms and of inter-arm regions. The inter-arm region appears as a trough of the brightness temperature in the shock model. An observed trough on aT b (l, v) diagram atl=80°–100°,v=−20 km s−1 is reproduced reasonably well by the shock model, while the linear model fails to reproduce it. Effects of the galactic shocks on the terminal velocity is also discussed.

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Sawa, T. Neutral hydrogen in the Galaxy and the galactic shocks. Astrophys Space Sci 53, 467–478 (1978).

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  • Hydrogen
  • Linear Model
  • Brightness Temperature
  • Tangential Direction
  • Terminal Velocity