A Minisurvey of Interstellar Titanium from the Southern Hemisphere

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Abstract

We describe the results of a minisurvey of interstellar Ti II and Ca II absorption toward 42 early-type stars observed from the southern hemisphere at a spectral resolution of 4.5 km s-1. Results are also presented for the Na I ultraviolet line (3302 Å) detected toward nine of these targets. We examine the dependence of the integrated column densities of N(Ti II), N(Ca II), and N(Na I) on distance, reddening, neutral hydrogen column density, and their Galactic elemental abundance. Our findings support the proposition that Ti II and Ca II absorption originates in the same regions of the pervasive, warm, and neutral intercloud gas of the interstellar medium. We have observed a correlation of decreasing Ti and Ca abundance with increasing line-of-sight gas density. The Ti II/Ca II abundance ratio has been found to be essentially constant under all the interstellar density conditions we have sampled. Thus, we conclude that the general absorption properties of titanium (and calcium) are similar throughout the entire disk of our Galaxy.

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