Abstract
We have determined the metallicity of the zabs = 1.0093 damped Lyman α system in the bright QSO EX 0302-223; this is only the third such measurement at redshifts z ≲ 1. Unlike the previous two cases, we find that the abundance of Zn is only a factor of ∼ 2 lower than in the Galactic interstellar medium today and is entirely compatible with the typical metallicity of stars in the Milky Way disk at a look-back time of 9.5 Gyrs. Although the galaxy responsible for producing the absorption system has yet to be positively identified, our observations show that galaxies on a chemical evolution path similar to that of the Milky Way do contribute to the damped Lyman a population at intermediate redshifts. Cr is 2.5 times less abundant than Zn, presumably because of depletion onto dust; however, the degree of depletion is less severe than in diffuse interstellar clouds in the disk of our Galaxy and in the Magellanic Clouds. Evidently, the interstellar environment in damped Lyman a galaxies is less conducive to the formation and survival of dust grains (and molecular hydrogen), but the physical processes at the root of this effect have yet to be clarified.
Original language | English (US) |
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Pages (from-to) | 22-26 |
Number of pages | 5 |
Journal | Astronomy and Astrophysics |
Volume | 327 |
Issue number | 1 |
State | Published - 1997 |
Externally published | Yes |
All Science Journal Classification (ASJC) codes
- Astronomy and Astrophysics
- Space and Planetary Science
Keywords
- Galaxies: abundances
- Galaxies: ISM
- Quasar: absorption lines
- Quasar: individual: Ex 0302-223