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J.L. Linsky, B.E. Wood (JILA/Univ. Colorado)
Analyses of spectra obtained with the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite, together with previous Copernicus and IMAPS spectrometer observations, reveal a very wide range in the deuterium/hydrogen (D/H) ratios for interstellar gas in the Galactic disk within 1 kpc of the Sun. This result is very difficult to explain on the basis of nuclear processes in stars that convert deuterium to 3He and 4He and the infall of deuterium rich gas from the Galactic halo and the intergalactic medium, because the D/H ratios differ greatly on very short spatial scales. We argue instead that spatial variations in the depletion of deuterium onto dust grains can explain these local variations in the gas phase D/H ratios. The D/H measurements appear to fall into three regimes depending on the line of sight hydrogen column density. Our dynamic deuterium depletion model naturally explains the constant D/H measurements for the local Bubble (log N(HI) < 19.2), the wide range of gas phase D/H ratios found in the intermediate regime (log N(HI) = 19.2-20.5), and the low gas phase D/H ratios at larger hydrogen column densities. We argue that the most representative value for the total (gas plus dust) D/H ratio within 1 kpc of the Sun is 23 +/- 4 ppm (parts per million), which constrains Galactic chemical evolution models to have small deuterium astration rates.
This work is based on observations made with the NASA-CNES-CSA Far Ultraviolet Spectroscopic Explorer. FUSE is operated for NASA by the Johns Hopkins University under NASA contract NAS5-32985.
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Bulletin of the American Astronomical Society, 36 #2
© YEAR. The American Astronomical Soceity.