UVES observations of QSO 0000-2620: Oxygen and zinc abundances in the damped Ly alpha galaxy at z(abs)=3.3901

Observations of the QSO 0000-2620 with the Ultraviolet-Visual Echelle Spect rograph at the 8.2 m ESO Kueyen telescope are used for abundance analysis o f the damped Ly alpha system at z(abs) = 3.3901. Several oxygen lines are i dentified in the Lya forest, and a measure for the oxygen abundance is obta ined at [O/H] = -1.85 +/- 0.15 by means of the unsaturated O I lambda 925 a nd O I lambda 950 lines. This represents the most accurate O measurement in a damped Lya galaxy so far. We have also detected Zn II lambda 2026 and Cr II lambda lambda 2056, 2062 redshifted at approximate to 8900 Angstrom and found abundances [Zn/H] = -2.07 +/- 0.10 and [Cr/H] = - 1.99 +/- 0.09. Fur thermore, previous measurements of Fe, Si, Ni, and N have been refined, yie lding [Fe/H] = -2.04 +/- 0.09, [Si/H] = -1.90 +/- 0.08, [Ni/H] = -2.27 +/- 0.09, and [N/H] = -2.68 +/- 0.12. The abundance of the nonrefractory elemen t zinc is the lowest among the damped Ly alpha systems, showing that the as sociated intervening galaxy is indeed in the early stages of its chemical e volution. The fact that the Zn abundance is identical to that of the refrac tory elements Fe and Cr suggests that dust grains have not formed yet. In t his damped Lya system the observed [O, S, Si/Zn, Fe, Cr] ratios, in whateve r combination are taken, are close to solar (i.e., 0.1-0.2 dex) and do not show the [alpha-element/Fe] enhancement observed in Milky Way stars of comp arable metallicity. The observed behavior supports a galaxy evolution model characterized by either episodic or low star formation rate rather than a Milky Way-type evolutionary model.