The Deuterium, Oxygen, and Nitrogen Abundance toward LSE 44

Abstract

We present measurements of the column densities of interstellar D i, O i, N i, and H 2 made with the Far Ultraviolet Spectroscopic Explorer (FUSE ) and of H i made with the International Ultraviolet Explorer (IUE ) toward the sdO star LSE 44 [(l;. This target is among the seven most distant Galactic sight lines for which these abundance ratios have been measured. The H i column density was estimated by fitting the damping wings of interstellar Ly. The column densities of the remaining species were determined with profile fitting analyses and supplemented with curve-of-growth analyses for O i and H 2 . We find log N (D i) ¼ 15:87 AE 0:08, log N (O i) ¼

THE NEW DETECTIONS OF7Li/6Li ISOTOPIC RATIO IN THE INTERSTELLAR MEDIA

“…Concerning isotopic ratios, Penzias (1979) reported that the D/H abundance ratio shows an appreciable gradient with respect to R G from the Galactic center to outside the solar orbit, i.e., 0 kpc R G 12 kpc, with an anomaly in D/H near the Galactic center (Wannier 1980;Lubowich et al 2000). Recent observational studies of D/H in the local ISM reported a uniform single value D/H ∼ 1.5 × 10 −5 within the Local Bubble (Moos et al 2002;Oliveira et al 2003), although variations of factors of 2 or so is also observed in the distant ISM beyond the Local Bubble Wood et al 2004;Hébrard et al 2005;Friedman et al 2006). From a theoretical viewpoint, Prantzos (1996) proposed a chemical evolution model of the Galactic disk with each ring of appropriate width at different Galactocentric distance R G evolving independently under an assumption of homogeneous mixing and instantaneous recycling of the ISM.…”

Variations in D/H and D/O from NewFar Ultraviolet Spectroscopic ExplorerObservations

“…The fraction of H 2 along these sight BD +39 3226, and TD1 32709, respectively. Hence, for the three sight lines, Friedman et al 2006).…”

What the D/O ratio tells us about the interstellar abundance of deuterium?

“…(D/H) LB is not representative of the cosmic material at the present epoch. Indeed, in addition to the early Copernicus results reported above, FUSE has provided extra clues for a significant dispersion in (D/H) ISM beyond the Local Bubble (Friedman et al 2002;Hoopes 62 G. Hébrard et al 2003;Wood et al 2004;Williger et al 2005;Hébrard et al 2005;Friedman et al 2006;Oliveira & Hébrard 2006;Dupuis et al 2009 If a (D/H) ISM canonical value exists, the best way to determine it might be to measure deuterium along the long lines of sight with high column densities. More material is probed, and thus localized anomalies are likely to be averaged out.…”

“…The probable cause is the N (OI) measurements, performed with the λ1302Å saturated transition in the HST spectra, whereas N (OI) is measured from unsaturated lines in the FUSE bandpass. Hébrard et al (2005) and Friedman et al (2006) have shown examples of systematic effects on column densities due to saturated lines.…”

“…Indeed, D/H and D/O measurements are presently available for 9 distant targets (i.e. clearly outside the Local Bubble) : HD 195965 and HD 191877 (Hoopes et al 2003), LSS 1274 (Hébrard & Moos 2003;Wood et al 2004), JL 9 (Wood et al 2004, PG 0038+199 (Williger et al 2005), HD 90087 , LSE 44 (Friedman et al 2006), HD 41161 and HD 53975 (Oliveira & Hébrard 2006). The χ 2 are 35.8 for D/H and 5.9 for D/O, for 8 degrees of freedom.…”