This investigation is aimed at clarifying the nature of the interstellar gas
seen in absorption against bright O and B stars. Towards this end we have
obtained for the first time HI absorption spectra towards radio sources very
close to the lines of sight towards 25 bright stars previously studied. In this
paper we describe the selection criteria, the details regarding our
observations, and finally present the absorption spectra. In the accompanying
paper we analyse the results and draw conclusions.Comment: 20 pages, 12 figures, accepted by Journal of Astrophysics and
  Astronom

Dwarakanath, K. S.

Rajagopal, Jayadev

Srinivasan, G.

English

arXiv

This investigation is aimed at clarifying the nature of the interstellar gas seen in absorption against bright O and B stars. Towards this end we have obtained for the first time HI absorption spectra towards radio sources very close to the lines of sight towards twenty five bright stars previously studied. In this paper we describe the selection criteria, the details regarding our observations, and finally present the absorption spectra. In the accompanying paper we analyse the results and draw conclusions

Dwarakanath, K.S.

Raman Research Institute Digital Repository

Journal of Astrophysics and Astronomy

The interstellar clouds of Adams and Blaauw revisited: An HI absorption  study - I

In the preceding paper (Paper I), we presented HI absorption spectra towards radio sources very close to the lines of sight towards twenty five bright stars against which optical absorption spectra had been obtained earlier, In this paper we analyse the results and draw some conclusions. To summarize briefly, in most cases we found HI absorption at velocities corresponding to the optical absorption features provided one restricted oneself to velocities ≲10 kms−1. At higher velocities we did not detect any HI absorption down to an optical depth limit of 0.1 (except in four cases which we attribute to gas in systematic motion rather than clouds in random motion). After discussing various scenarios, we suggest that this trend should perhaps be understood in terms of the high velocity interstellar clouds being accelerated, heated and ablated by expanding supernova remnants

Publications of the IAS Fellows

The interstellar clouds of Adams and Blaauw revisited: an HI absorption study - II

In the preceding paper (Paper I), we presented HI absorption spectra towards radio sources very close to the lines of sight towards twenty-five bright stars against which optical absorption spectra had been obtained earlier. In this paper we analyse the results and draw some conclusions. To summarize briefly, in most cases we found HI absorption at velocities corresponding to the optical absorption features provided one restricted oneself to velocities < 10 km s-1. At higher velocities we did not detect any HI absorption down to an optical depth limit of 0.1 (except in four cases which we attribute to gas in systematic motion rather than clouds in random motion). After discussing various scenarios, we suggest that this trend should perhaps be understood in terms of the high velocity interstellar clouds being accelerated, heated and ablated by expanding supernova remnants

The interstellar clouds of Adams and Blaauw revisited: an HI absorption study - I

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Raman Research Institute Digital Repository