The most metal-rich intervening quasar absorber known

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-α systems (DLAs). Surprisingly, the global mean metallicity derived from DLAs is about 1/10th solar at leading to the so-called “missing-metals problem”. In this paper, we present high-resolution observations of a sub-DLA system at z_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, , [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 ∼3 and ∼35, respectively, indicating non-uniform dust depletion. Mn/Fe is super-solar in almost all components, and varies by a factor of 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.