A New FUSE Survey of Interstellar HD
Abstract
We have used archival FUSE data to complete a survey of interstellar HD in 41 lines of sight with a wide range of extinctions. This follow-up to an earlier survey was made to further assess the utility of HD as a cosmological probe; to analyze the HD formation process; and to see what trends with other interstellar properties were present in the data. We employed the curve-of-growth method, supported by line profile fitting, to derive accurate column densities of HD. We find that the N(HD)/2N(H2) ratio is substantially lower than the atomic D/H ratio and conclude that the molecular ratio has no bearing on cosmology, because local processes are responsible for the formation of HD. Based on correlations with E(B - V) , H2, CO, and iron depletion, we find that HD is formed in the densest portion of the clouds; the slope of the log N(HD)/log N(H2) correlation is greater than 1.0, caused by the destruction rate of HD declining more slowly than that of H2; and, as a sidelight, that the depletions are density dependent.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2008
- DOI:
- 10.1086/592288
- arXiv:
- arXiv:0808.0926
- Bibcode:
- 2008ApJ...688.1124S
- Keywords:
-
- ISM: abundances;
- Astrophysics
- E-Print:
- 30 pages, 13 figures