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The Ionization and Metallicity of the Intervening O VI Absorber at z = 0.1212 in the Spectrum of H1821+643
- Source :
- The Astrophysical Journal; December 2001, Vol. 563 Issue: 2 p724-735, 12p
- Publication Year :
- 2001
-
Abstract
- We use high-resolution UV spectra of the radio-quiet quasar (QSO) H1821+643 (zem = 0.297), obtained with the Space Telescope Imaging Spectrograph (STIS) and the Far Ultraviolet Spectroscopic Explorer (FUSE), to study the ionization and metallicity of an intervening O VI absorption line system at zabs = 0.1212. This absorber has the following notable properties: (1) several galaxies are close to the sight line at the absorber redshift, including an actively star-forming galaxy at a projected distance of 144 himg1.gif kpc, (2) there is a complex cluster of H I Lya absorption lines near the O VI redshift, including at least five components spread over a velocity range of ~700 km s-1, (3) the strongest Lya line in the cluster appears to be composed of a mildly saturated component with a typical b-value blended with a remarkably broad component with b [?] 85 km s-1, (4) the O VI absorption is not aligned with the strongest (saturated) H I absorption, but instead is well aligned with the very broad component, and (5) the only detected species (at the 4 s level) are O VI and H I, despite coverage of strong transitions of abundant elements (e.g., C II, C III, and C IV). Based on these constraints, we find that the absorption line properties can be produced in collisionally ionized gas with 105.3 [?] T [?] 105.6 K and -1.8 [?] [O/H] [?] -0.6. However, we find that photoionization is also viable if the path length l through the absorbing gas is long enough; simple photoionization models require 85 [?] l [?] 1900 kpc and -1.1 [?] [O/H] [?] -0.3. We briefly discuss how observations of X-ray absorption lines due to O VII and O VIII could be used, in principle, to break the ionization mechanism degeneracy, and we conclude with some comments regarding the nature of O VI absorbers.
Details
- Language :
- English
- ISSN :
- 0004637X and 15384357
- Volume :
- 563
- Issue :
- 2
- Database :
- Supplemental Index
- Journal :
- The Astrophysical Journal
- Publication Type :
- Periodical
- Accession number :
- ejs18555818