1994/10/24 by K. Lipman, Keith Lipman, Max Pettini · 2 citations
Physics and Astronomy · #Astrophysics and Star Formation Studies #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies #astro-ph
paper · pdf · doi:10.1086/175466
Accepted for publication in ApJ, due to appear 1 April 1995. 23 pages including 5 figures; uuencoded compressed postscript; RG0-212
arxiv created 1994/10/24 · openalex publication_date 1995/04/01 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We present observations of Ti~II~λ3384 absorption towards 15 distant stars in the Galactic halo and the Magellanic Clouds. These new data extend existing surveys of the distribution of Ti+ to larger distances from the plane of the Galaxy than sampled previously, allowing the scale height of titanium to be determined for the first time. We find hTi+ = 1.5 ± 0.2~kpc, a value which although greater than those of other tracers of neutral gas, is not as large as had been suspected. We interpret the extended distribution of Ti+ as an indication that its severe depletion in interstellar clouds in the disk is reduced at the lower densities prevailing in the halo. The data are consistent with a simple power-law dependence of the Ti abundance on the ambient density, with exponent k ≃ -1. If the model is correct, it implies that refractory elements like Ti are fully returned to the gas phase at distances beyond ∼ 1 kpc from the plane of the Galaxy.