The translucent molecular clouds toward hd 154368 .1. Extinction, abundances, and depletions

Snow, T. P. and Black, J. H. and vanDishoeck, E. F. and Burks, G. and Crutcher, R. M. and Lutz, Barry L. and Hanson, M. M. and Shuping, R. Y. (1996) The translucent molecular clouds toward hd 154368 .1. Extinction, abundances, and depletions. Astrophysical Journal, 465 (1). pp. 245-263. ISSN 1538-4357

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Abstract

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 09.5 Iab 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 Angstrom, 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 zeta 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.

Item Type:	Article
Publisher’s Statement:	© 1996 The American Astronomical Society. Provided by the NASA Astrophysics Data System.
ID number or DOI:	10.1086/177416
Keywords:	absorption-lines; dust, extinction; high-resolution observations; interstellar abundances; ISM, abundances; ISM, clouds; ISM, molecules; oscillator-strengths; rho-ophiuchi cloud; si-ii; southern ob stars; stars, individual (HD 154368); ultraviolet extinction; ultraviolet, ISM; uv extinction; zeta-ophiuchi
Subjects:	Q Science > QB Astronomy
NAU Depositing Author Academic Status:	Faculty/Staff
Department/Unit:	College of Engineering, Forestry, and Natural Science > Physics and Astronomy
Date Deposited:	30 Sep 2015 17:51
URI:	http://openknowledge.nau.edu/id/eprint/429

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