The translucent molecular clouds toward HD 154368. I. Extinction, abundances, and depletions

Theodore P. Snow, John H. Black, Ewine F. Van Dishoeck, Geoffrey Burks, Richard M. Crutcher, Barry L. Lurz, Margaret M. Hanson, Ralph Y. Shuping

Research output: Contribution to journalArticlepeer-review


We report the results of a comprehensive analysis of a line of sight observed using the Goddard High Resolution Spectrograph (GHRS) on the Hubble Space Telescope (HST), toward HD 154368, an O9.5 lab star located about 800 pc away. The line of sight intersects translucent interstellar cloud material, having a color excess E(B-V) = 0.82 and known high molecular abundances from ground-based data. The HST observations consist of high-resolution spectra obtained with grating ECH-B at wavelengths longward of 1800 Å, and moderate-resolution spectra from grating G160M at shorter wavelengths. We observed some 19 wavelength settings, covering the positions of numerous atomic and molecular transitions. We also incorporate IUE and ground-based data in the study, the latter coming from several observatories at visible and millimeter wavelengths. In this paper we report on the general goals and results of the study, with emphasis on the atomic abundances and depletions. We find that the column densities of most species are slightly higher, relative to the adopted total gas column density, than in some thinner clouds in which most of the absorption arises in a single dense component. Consequently the depletions of elements from the gas phase onto the dust are less than in "typical" diffuse clouds such as the one toward ζ Oph. Most of the gas toward HD 154368 resides in two main clouds, centered near -3.26 and -20.95 km s-1 (heliocentric). Our profile analyses show that the depletions in these two clouds are similar. We discuss the possible relationship of this result to the ultraviolet extinction curve toward HD 154368, derived from IUE spectra.

Original languageEnglish (US)
Pages (from-to)245-263
Number of pages19
JournalAstrophysical Journal
Issue number1 PART I
StatePublished - 1996


  • Dust, extinction
  • ISM: Abundances
  • ISM: Clouds
  • ISM: Molecules
  • Stars: Individual (HD 154368)
  • Ultraviolet: ISM

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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