ELEMENT ABUNDANCES IN A GAS-RICH GALAXY AT z = 5: CLUES TO THE EARLY CHEMICAL ENRICHMENT OF GALAXIES

Element abundances in high-redshift quasar absorbers offer excellent probes of the chemical enrichment of distant galaxies, and can constrain models for population III and early population II stars. Recent observations indicate that the sub-damped Ly α (sub-DLA) absorbers are more metal-rich than DLA absorbers at redshifts 0 4.5 and no sub-DLAs at z > 3.5 have “dust-free” metallicity measurements of undepleted elements. We report the first quasar sub-DLA metallicity measurement at z > 3.5, from detections of undepleted elements in high-resolution data for a sub-DLA at z = 5.0. We obtain fairly robust abundances of C, O, Si, and Fe, using lines outside the Ly α forest. This absorber is metal-poor, with [O/H] = −2.00 ± 0.12, which is ≳4 σ below the level expected from extrapolation of the trend for z