Discovery of a Damped Lyα Galaxy at z ∼ 3 toward the Quasar SDSS J011852+040644

We report the detection of the host galaxy of a damped Lyα system (DLA) with log N(H i) [cm-2] = 21.0 ± 0.10 at z ≈ 3.0091 toward the background quasar SDSS J011852+040644 using the Palomar Cosmic Web Imager at the Hale (P200) telescope. We detect Lyα emission in the dark core of the DLA trough at a 3.3σ confidence level, with Lyα luminosity of L Lyα = (3.8 ± 0.8) × 1042 erg s-1, corresponding to a star formation rate of ⪆2 M o˙ yr-1 (considering a lower limit on Lyα escape fraction ∫escLyα ∼ 2%) as typical for Lyman break galaxies at these redshifts. The Lyα emission is blueshifted with respect to the systemic redshift derived from metal absorption lines by 281 ± 43 km s-1. The associated galaxy is at very small impact parameter of ≲12 kpc from the background quasar, which is in line with the observed anticorrelation between column density and impact parameter in spectroscopic searches tracing the large-scale environments of DLA host galaxies.