Journal Article

Interstellar Ti <span class="smallCaps">ii</span> in the Milky Way and Magellanic Clouds*

Daniel E. Welty and Paul A. Crowther

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 404, issue 3, pages 1321-1348
Published in print May 2010 | ISSN: 0035-8711
Published online May 2010 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.16386.x
Interstellar Ti ii in the Milky Way and Magellanic Clouds*

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We discuss several sets of Ti ii absorption-line data, which probe a variety of interstellar environments in our Galaxy and in the Magellanic Clouds. Comparisons of high-resolution [full width at half-maximum (FWHM) ∼ 1.3–1.5 km s−1] Ti ii spectra of Galactic targets with corresponding high-resolution spectra of Na i, K i and Ca ii reveal both similarities and differences in the detailed structure of the absorption-line profiles – reflecting component-to-component differences in the ionization and depletion behaviour of those species. Moderate-resolution (FWHM ∼ 3.4–4.5 km s−1) spectra of more heavily reddened Galactic stars provide more extensive information on the titanium depletion in colder, denser clouds – where more than 99.9 per cent of the Ti may be in the dust phase. Moderate-resolution (FWHM ∼ 4.5–8.7 km s−1) spectra of stars in the Magellanic Clouds suggest that the titanium depletion is generally much less severe in the Large and Small Magellanic Clouds than in our Galaxy [for a given N(Htot), E(BV), or molecular fraction f(H2)]– providing additional evidence for differences in depletion patterns in those two lower-metallicity galaxies. We briefly discuss possible implications of these results for the interpretation of gas-phase abundances in quasi-stellar object absorption-line systems and of variations in the D/H ratio in the local Galactic interstellar medium.

Keywords: ISM: abundances; ISM: lines and bands; galaxies: ISM; Magellanic Clouds

Journal Article.  23493 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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