Kinematics and star formation activity in the zabs = 2.03954 damped Lyman-alpha system towards PKS 0458-020

International audienceWe present UVES observations of the log N(H i) = 21.7 damped Lyman-alpha system at z_abs = 2.03954 towards the quasar PKS 0458-020. H i Lyman-alpha emission is detected in the center of the damped Lyman-alpha absorption trough. Metallicities are derived for Mg ii, Si ii, P ii, Cr ii, Mn ii, Fe ii and Zn ii and are found to be -1.21±0.12, -1.28±0.20, -1.54±0.11, -1.66±0.10, -2.05±0.11, -1.87±0.11, -1.22±0.10, respectively, relative to solar. The depletion factor is therefore of the order of [Zn/Fe] = 0.65. We observe metal absorption lines to be blueshifted compared to the Lyman-alpha emission up to a maximum of ~100 and 200 km s-1 for low and high-ionization species respectively. This can be interpreted either as the consequence of rotation in a large (~7 kpc) disk or as the imprint of a galactic wind. The star formation rate (SFR) derived from the Lyman-alpha emission, 1.6 M&sun; yr-1, is compared with that estimated from the observed C ii* absorption. No molecular hydrogen is detected in our data, yielding a molecular fraction log f < -6.52. This absence of H2 can be explained as the consequence of a high ambient UV flux which is one order of magnitude larger than the radiation field in the ISM of our Galaxy and originates in the observed emitting region