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Optical interstellar lines in dark clouds

Cohen, Judith G. (1973) Optical interstellar lines in dark clouds. Astrophysical Journal, 186 . pp. 149-163. ISSN 0004-637X. doi:10.1086/152483.

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Observations of the equivalent widths and radial velocities of the interstellar lines of Ca ii, Na i, CH, and CH^+ are presented for 30 stars. A special effort was made to observe stars behind or within dense clouds with up to 3 mag of absorption. The interstellar lines in the cloud stars are compared with those in a group of highly reddened supergiants whose reddening arises from a large distance, i.e., a long path length through relatively thin material. The atomic interstellar lines of the cloud stars are weak compared to those of supergiants with the same color excess; the molecular lines are of comparable strength in the two groups, except that the ratio n_(CH)/n_(CH^+) is larger in the cloud stars. The ionization equilibrium is discussed, and it is concluded that the deficiency of atomic Ca and Na relative to hydrogen in the clouds is about a factor of 100 larger than in the supergiants.

Item Type:Article
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Cohen, Judith G.0000-0002-8039-4673
Additional Information:© American Astronomical Society • Provided by the NASA Astrophysics Data System. Received 1973 April 12; revised 1973 June 18. I am very grateful to the Hale Observatories for generous allotments of telescope time and to Drs. G. Grasdalen, C. Heiles, S. Strom, Mr. L. Carrasco, and an anonymous referee for helpful comments. Dr. F. Chaffee has discussed his unpublished observational material. The Miller Institute for Basic Research has provided financial support.
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Miller Institute for Basic Research in ScienceUNSPECIFIED
Subject Keywords:abundances, nebular — interstellar matter — molecules, interstellar — nebulae
Record Number:CaltechAUTHORS:20190529-103834518
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:95880
Deposited By: George Porter
Deposited On:29 May 2019 20:26
Last Modified:16 Nov 2021 17:16

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