Variations in D/H and D/O from New Far Ultraviolet Spectroscopic Explorer Observations

• Published in: The Astrophysical journal Vol. 642; no. 1; pp. 283 - 306
• Main Authors: Oliveira, Cristina M, Moos, H. Warren, Chayer, Pierre, Kruk, Jeffrey W
• Format: Journal Article
• Language: English
• Published: Chicago, IL IOP Publishing 01-05-2006; University of Chicago Press
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; Abundance; stars: individual (WD 1034+001, BD +39 3226, TD1 32709); ultraviolet: ISM; ISM: evolution; FUSE satellite; ISM: abundances
• ISSN: 0004-637X; 1538-4357
• DOI: 10.1086/500962

We use data obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) to determine the interstellar abundances of D I, N I, O I, Fe II, and H sub(2) along the sight lines to WD 1034+001, BD +39 3226, and TD1 32709. Our main focus is on determining the D/H, N/H, O/H, and D/O ratios along these sight lines, with log iV(H) > 20.0, that probe gas well outside of the Local Bubble. Hubble Space Telescope (HST) and International Ultraviolet Explorer (IUE) archival data are used to determine the H I column densities along the WD 1034+001 and TD1 32709 sight lines, respectively. For BD +39 3226, a previously published N(H I) is used. We find (D/H) x 10 super(5) = 2.14 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(5) sub(4) super(3) sub(5), 1.17 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(3) sub(2) super(1) sub(5), and 1.86 super(+) sub(-) super(0) sub(0) super(.) sub(.) super(5) sub(4) super(3) sub(3) and (D/O) x 10 super(2) = 6.31 super(+) sub(-) super(1) sub(1) super(.) sub(.) super(7) sub(3) super(9) sub(8), 5.62 super(+) sub(-) super(1) sub(1) super(.) sub(.) super(6) sub(3) super(1) sub(1), and 7.59 super(+) sub(-) super(2) sub(1) super(.) sub(.) super(1) sub(7) super(7) sub(6) for the WD 1034+001, BD+39 3226, and TD1 32709 sight lines, respectively (all 1 s). The scatter in these three D/H ratios exemplifies the scatter that has been found by other authors for sight lines with column densities in the range 19.2 < log N(H) < 20.7. The D/H ratio toward WD 1034+001 and all of the D/O ratios derived here are inconsistent with the Local Bubble value and are some of the highest in the literature. We discuss the implications of our measurements for the determination of the present-epoch abundance of deuterium and for the different scenarios that try to explain the D/H variations. We present a study of D/H as a function of the average sight line gas density, using the ratios derived in this work as well as ratios from the literature, which suggests that D/H decreases with increasing gas volume density. Similar behaviors by other elements such as Fe and Si have been interpreted as the result of depletion into dust grains.