Zinc as a tracer of metallicity in the interstellar medium

The relative gas-phase abundance of zinc in the interstellar medium has been studied using high-resolution spectra from the IUE data bank of early-type stars with distances of up to 3 kpc. The chosen sight-lines all have measured N(H) values derived from Copernicus observations. Results show that in the H column density range of 5 x 1019 to 5 x 1021 cm-2 the relative gas-phase abundance of zinc is constant and slightly lower than the adopted solar abundance. No variation of zinc abundance with colour excess is evident. It follows that zinc can be used as a reliable tracer of metallicity in the interstellar medium. (author)