Optical interstellar lines in southern supergiants
Photoelectric photometry of 35 southern supergiants reveals a good correlation of the central residual intensity of the diffuse interstellar line at 4430 Å with color excess. From spectra of the brighter southern supergiants, I have derived column densities of Na i and Ca ii, and, in a few cases, of CH and CH^+. These results are averaged and compared with previous studies of the interstellar medium at high galactic latitudes and in the denser regions of the plane. The basic peculiarities of the interstellar lines in these two regions, as discussed in Papers I and II, are more sharply delineated by this comparison. Models for the gas in the halo are derived, and I obtained the mass of gas in the halo (from 1 x 10^7 to 6 x 10^7 M_⊙) and a maximum value of the metal depletion of the halo gas relative to the disk gas (from 300 to 90, depending on whether grains exist in the halo). This maximum value implies that the gas in the halo has been significantly contaminated by material which has undergone nuclear processing.
Additional Information© American Astronomical Society • Provided by the NASA Astrophysics Data System. Received 1974 August 26; revised 1974 October 7. The author is grateful to the staff at CTIO for a pleasant and fruitful visit. I thank the Director of Hale Observatories for time as a guest observer. This research was supported in its initial stages by the Miller Foundation of the University of California at Berkeley.
Published - 1975ApJ___197__117C.pdf