EDP Sciences
Free Access
Issue
A&A
Volume 404, Number 2, June III 2003
Page(s) 449 - 463
Section Extragalactic astronomy
DOI https://doi.org/10.1051/0004-6361:20030493


A&A 404, 449-463 (2003)
DOI: 10.1051/0004-6361:20030493

Photoionized $\ion{O}{vi}$ absorbers toward the bright QSO HE 0515-4414

S. A. Levshakov1, I. I. Agafonova1, D. Reimers2 and R. Baade2

1  Department of Theoretical Astrophysics, Ioffe Physico-Technical Institute, 194021 St. Petersburg, Russia
2  Hamburger Sternwarte, Universität Hamburg, Gojenbergsweg 112, 21029 Hamburg, Germany

(Received 20 December 2002 / Accepted 31 March 2003)

Abstract
We report on detailed Monte Carlo inversion analysis of five $\ion{O}{vi}$ systems from the spectrum of the bright quasar HE 0515-4414 ( $z_{\rm em}\,$= 1.71). The associated system at $z_{\rm abs}\,$= 1.697 with the neutral hydrogen column density N( $\ion{H}{i}$) $= 4.4\times10^{13}$ cm -2 shows pronounced absorption from highly ionized transitions of $\ion{C}{iii}$, $\ion{C}{iv}$, $\ion{N}{v}$, $\ion{O}{vi}$, $\ion{Si}{iv}$, and probably $\ion{S}{vi}$. We found that only a power law type ionizing spectrum ( $J_\nu \propto \nu^{-1.5}$) is consistent with the observed sample of the line profiles, i.e. the system is definitely intrinsic. The relative metal abundances give almost the solar pattern and the metallicity of ~5 times solar. The system originates in a thin shell of the line-of-sight thickness $L \la 16$ pc. Two $\ion{O}{vi}$ systems at $z_{\rm abs}\,$= 1.674 ([C/H] $\simeq -1.6$) and 1.602 ([O/H] $\simeq -1.1$), arising in intervening halos, have linear sizes of $L \simeq$ 3-14 kpc and $\simeq$17 kpc, respectively. Absorption systems at $z_{\rm abs}\,$= 1.385 ([C/H] $\simeq -0.3$, $L \simeq$ 1.7-2.5 kpc) and $z_{\rm abs}\,$= 1.667 ([C/H] $ \simeq -0.5$, $L \simeq 1$ kpc) exhibit characteristics very similar to that observed in metal-enriched high velocity clouds in the Milky Way. These systems are probably embedded in extremely metal-poor halos with [C/H] < -2.4 ( $z_{\rm abs}\,$= 1.667) and [C/H] < -3.7 ( $z_{\rm abs}\,$= 1.385). We also found two additional extremely metal-poor Ly $\alpha$ systems at $z_{\rm abs}\,$= 1.500 and 1.681 with, respectively, N( $\ion{H}{i}$) $\simeq 1.7\times10^{15}$ and $1.8\times10^{15}$ cm -2 and [C/H] < -4.0 and <-3.0, - an indication that the distribution of metals in the metagalactic medium is utterly patchy. Our results show that the ionization states in the analyzed $\ion{O}{vi}$ absorbers, ranging from $z \simeq 1.4$ to 1.7, can be maintained by photoionization only and that the fraction of the shock-heated hot gas with temperature $T_{\rm kin} > 10^5$ K is negligible in these systems.


Key words: cosmology: observations -- line: formation -- line: profiles -- quasars: absorption lines -- quasars: individual: HE 0515-4414

Offprint request: S. A. Levshakov, lev@astro.ioffe.rssi.ru

SIMBAD Objects



© ESO 2003

Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.

Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.

Initial download of the metrics may take a while.