UVES observations of a damped Lyα system at towards the quasar APM BR J0307-4945^*

¹ European Southern Observatory, Karl-Schwarzschildstr. 2, 85748 Garching bei München, Germany
² Observatoire de Genève, 1290 Sauverny, Switzerland
³ Institute of Astronomy, Madingley Road, Cambridge CB3 0HA, UK
⁴ Osservatorio Astronomico di Trieste, Via G.B. Tiepolo 11, 34131 Trieste, Italy
⁵ SIRTF Science Center, California Institute of Technology, MS 100-22, Pasadena, CA, USA

Corresponding author: M. Dessauges-Zavadsky, mdessaug@eso.org

Received: 14 September 2000
Accepted: 2 February 2001

Abstract

We present the first high-resolution (6.2 to 7.7 km s^-1 FWHM) spectra of the APM BR J0307-4945 quasar at obtained with UVES on the 8.2 m VLT Kueyen telescope. We focus our analysis on a damped Lyα (DLA) system at with a neutral hydrogen column density N(Hi) cm^-2. It is the most distant DLA system known to the present date, observed when the age of the universe was only 1.3 Gyr. It shows complex low- and high-ionization line profiles spanning ≈240 and 300 km s^-1 in velocity space respectively. We derive accurate abundances for N, O, Al, Si and Fe, and place a lower limit on C and an upper limit on Ni: [N/H] , [O/H] , [Al/H] , [Si/H] , [Fe/H] , [C/H] and [Ni/H] . The derived high metallicity, ~1/90 solar, shows that this very young absorber (≤1.3 Gyr) has already experienced a significant metal enrichment. The [O/Si] ratio is nearly solar suggesting a limited amount of dust, the relative [Si, O/Fe] abundance ratios show a similar enhancement as observed in the Milky Way stars with comparable metallicities, and the [N/O] ratio is very low. All these results point to an enrichment pattern dominated by type II supernovae which suggests a Milky Way type evolutionary model.