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Evidence for Correlated Titanium and Deuterium Depletion in the Galactic ISM

Jason X. Prochaska·Todd M. Tripp·J. Christopher Howk
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Abstract

Current measurements indicate that the deuterium abundance in diffuse interstellar gas varies spatially by a factor of ~4 among sightlines extending beyond the Local Bubble. One plausible explanation for the scatter is the variable depletion of D onto dust grains. To test this scenario, we have obtained high signal-to-noise, high resolution profiles of the refractory ion TiII along seven Galactic sightlines with D/H ranging from 0.65 to 2.1x10^-5. These measurements, acquired with the recently upgraded Keck/HIRES spectrometer, indicate a correlation between Ti/H and D/H at the >95% c.l. Therefore, our observations support the interpretation that D/H scatter is associated with differential depletion. We note, however, that Ti/H values taken from the literature do not uniformly show the correlation. Finally, we identify significant component-to-component variations in the depletion levels among individual sightlines and discuss complications arising from this behavior.

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Jason X. Prochaska, Todd M. Tripp, J. Christopher Howk. 2005-01-03. Evidence for Correlated Titanium and Deuterium Depletion in the Galactic ISM. https://doi.org/10.1086/428436

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