Interstellar zinc revisited : possible depletion in high density sight-lines.

Abstract

The question of the nondepletion of interstellar zinc has been reexamined in light of recent results which show that the depletions of many elements, including the volatile element chlorine, show better correlations with the mean volume density of hydrogen, than with hydrogen column density. Zinc abundances from an earlier study have been combined with newly derived data for high mean density sight-lines. Although the data quality is insufficient to rule out the possibility that zinc is universally undepleted, the results are consistent with a trend of decreasing gas-phase abundance with increasing mean volume density of hydrogen. A possible interpretation in terms of a recently published model of interstellar gas distribution, and consequences for the use of zinc as a tracer of metallicity, are discussed.