Physics
Scientific paper
Apr 2004
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2004phdt.......195o&link_type=abstract
Thesis (PhD). THE JOHNS HOPKINS UNIVERSITY, Source DAI-B 64/10, p. 4986, Apr 2004, 157 pages.
Physics
Scientific paper
In this work we use data obtained with The Far Ultraviolet Spectroscopic Explorer and the Hubble Space Telescope to probe the abundance of deuterium in the local interstellar medium. The abundance of deuterium, relative to hydrogen (D/H), in the local interstellar medium provides a lower limit to the primordial abundance of deuterium, which is a key figure in testing the predictions of the standard big bang nucleosynthesis theory. In addition, measurements of the abundance of deuterium in the local interstellar medium are an important consistency check to test chemical evolution codes and their underlying assumptions. They challenge our understanding of stellar evolution and stellar mass loss, interstellar physics and rate of infall and chemical composition of halo gas. The primary goal of this work is to determine D/H. Since this is not always possible due to the lack of knowledge of the hydrogen column density, N(H), we will use the abundance of oxygen as surrogate for N(H), as the abundance of oxygen relative to hydrogen has been shown to be remarkably constant over a range of distances and physical conditions. In this work we analyze six lines of sight (GD 246, WD 2331+475, WD 0004+330, HZ 21, Lan 23, and PG 0038+199) probing different regions of the local interstellar medium, with varying amounts of molecular hydrogen. We perform a complete analysis of each line of sight, and determine the column densities of several atoms, ions and molecules. We use the apparent optical depth, curve of growth, and profile fitting techniques, when possible, to determine the column densities. We compute the ratios, whenever possible, of D I/H I, N I/H I, O I/H I, D I/N I, D I/O I, and O I/N I. We find that our results are in agreement with previously published results, derived with FUSE data, probing similar lines of sight. Using the results derived in this work together with previously published FUSE ratios for the local interstellar medium we compute revised FUSE mean ratios. We determine the following weighted means: D I/H I = (1.52 ± 0.07) × 10-5), N I/H I = (4.34 ± 0.31) × 10-5, O I/H I = (3.25 ± 0.33) × 10-4, D I/N I = (3.40 ± 0.22) × 10-1, D I/O I = (4.04 ± 0.24) × 10-2, and O I/N I = 8.20 ± 0.66, where the uncertainties quoted are the standard error in the mean.
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