Astrophysics and Space Science

, Volume 53, Issue 2, pp 467–478 | Cite as

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.


Hydrogen Linear Model Brightness Temperature Tangential Direction Terminal Velocity 
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Copyright information

© D. Reidel Publishing Company 1978

Authors and Affiliations

  • T. Sawa
    • 1
  1. 1.Astronomical InstituteTohoku UniversitySendaiJapan

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