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 logN(HD)/log(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.

30 pages, 13 figures; Accepted for publication in ApJ

References in corpus (8)

• A FUSE Survey of Interstellar Molecular Hydrogen in Translucent Clouds
• What is the Total Deuterium Abundance in the Local Galactic Disk?
• Ultraviolet Extinction Properties in the Milky Way
• Direct Measurement of the Ratio of Carbon Monoxide to Molecular Hydrogen in the Diffuse Interstellar Medium
• Deuterated molecular hydrogen in the Galactic ISM. New observations along seven translucent sightlines
• New Insights on Interstellar Gas-Phase Iron
• FUSE Observations of the HD Molecule toward HD 73882
• The role of carbon grains in the deuteration of H2

Cited by in corpus (19)

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• The determination of protoplanetary disk masses
• UV-driven chemistry in simulations of the interstellar medium. I. Post-processed chemistry with the Meudon PDR code
• HD/H2 Molecular Clouds in the Early Universe: The Problem of Primordial Deuterium
• Observations of a Magellanic Corona
• 3D chemical structure of diffuse turbulent ISM. I. Statistics of the HI-to-H${}_2$ transition
• HD molecules at high redshift: The absorption system at z=2.3377 towards Q 1232+082
• HD/H2 as a probe of the roles of gas, dust, light, metallicity and cosmic rays in promoting the growth of molecular hydrogen in the diffuse interstellar medium
• Thermal Pressures in the Interstellar Medium of the Magellanic Clouds
• A High Precision Survey of the D/H Ratio in the Nearby Interstellar Medium
• The low temperature D${}^{+}$ + H${}_2$ $\to$ HD + H${}^{+}$ reaction rate coefficient: a ring polymer molecular dynamics and quasi-classical trajectory study
• The Influence of Deuteration and Turbulent Diffusion on the Observed D/H Ratio
• HD molecules at high redshift: cosmic-ray ionization rate in the diffuse interstellar medium
• HD/H${}_2$ ratio in the diffuse interstellar medium
• Estimation of physical conditions in the cold phase of the ISM in the sub-DLA system at z = 2.06 in the spectrum of the quasar J2123-0050
• Mapping the Universe in HD
• Influence of radiative pumping on the HD rotational level populations in diffuse molecular clouds of the interstellar medium