The first detection of cobalt in a damped Lyman alpha system

The study of elemental abundances in damped Lyman alpha systems (DLAs) at h igh redshift represents one of our best opportunities to probe galaxy forma tion and chemical evolution at early times. By coupling measurements made i n high-z DLAs with our knowledge of abundances determined locally and with nucleosynthetic models, we can start to piece together the star formation h istories of these galaxies. Here, we discuss the clues to galactic chemical evolution that may be gleaned from studying the abundance of Co in DLAs. W e present high resolution echelle spectra of two quasi-stellar objects (QSO s), Q2206-199 and Q1223 + 17, both already known to exhibit intervening dam ped systems. These observations have resulted in the first ever detection o f Co at high redshift, associated with the Z(abs) = 1.92 DLA in the sightli ne towards Q2206-199. We find that the abundance of Co is approximately 1/4 solar and that there is a clear overabundance relative to iron, [Co/Fe] = +0.31 +/- 0.05. From the abundance of Zn, we determine that this is a relat ively metal-rich DLA, with a metallicity of approximately 1/3 Z.. Therefore , this first detection of Co is similar to the marked overabundance relativ e to Fe seen in Galactic bulge and thick-disc stars.