The most metal-rich intervening quasar absorber known

Free access article

Issue		A&A Volume 450, Number 1, April IV 2006


Page(s)		53 - 57
Section		Extragalactic astronomy
DOI		http://dx.doi.org/10.1051/0004-6361:20054642

A&A 450, 53-57 (2006)
DOI: 10.1051/0004-6361:20054642

The most metal-rich intervening quasar absorber known

C. Péroux¹, V. P. Kulkarni², J. Meiring², R. Ferlet³, P. Khare⁴, J. T. Lauroesch⁵, G. Vladilo⁶ and D. G. York⁷

¹ European Southern Observatory, Garching-bei-München, Germany
e-mail: cperoux@eso.org
² Dept. of Physics and Astronomy, Univ. of South Carolina, Columbia, USA
³ Institut d'Astrophysique de Paris, UMR7095 CNRS, Université Pierre & Marie Curie, France
⁴ Dept. of Physics, Utkal University, Bhubaneswar, India
⁵ Dept. of Physics and Astronomy, Northwerstern University, Evanston, USA
⁶ Osservatorio di Trieste, Trieste, Italy
⁷ Dept. of Astronomy and Astrophysics, Univ. of Chicago, Chicago, USA

(Received 17 August 2005 / Accepted 3 January 2006)

Abstract
The metallicity in portions of high-redshift galaxies has been successfully measured thanks to the gas observed in absorption in the spectra of quasars, in the Damped Lyman- $\alpha$ systems (DLAs). Surprisingly, the global mean metallicity derived from DLAs is about 1/10 ${\rm th}$ solar at $0\la z \la4$ leading to the so-called "missing-metals problem". In this paper, we present high-resolution observations of a sub-DLA system at $z_{\rm abs}$ = 0.716 with super-solar metallicity toward SDSS J1323-0021. This is the highest metallicity intervening high-H I quasar absorber currently known, and is only the second super-solar such absorber known to date. We provide a detailed study of this unique object from VLT/UVES spectroscopy. We derive [Zn/H] = +0.61, $\rm [Fe/H]=-0.51$ , [Cr/H] = < -0.53, [Mn/H] = -0.37, and [Ti/H] = -0.61. Observations and photoionisation models using the CLOUDY software confirm that the gas in this sub-DLA is predominantly neutral and that the abundance pattern is probably significantly different from a Solar pattern. Fe/Zn and Ti/Zn vary among the main velocity components by factors of $\sim$ 3 and $\sim$ 35, respectively, indicating non-uniform dust depletion. Mn/Fe is super-solar in almost all components, and varies by a factor of $\sim$ 3 among the dominant components. It would be interesting to observe more sub-DLA systems and determine whether they might contribute significantly toward the cosmic budget of metals.

Key words: galaxies: abundances -- intergalactic medium -- quasars: absorption lines -- quasars: individual: SDSS J1323-0021

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