Emission-line spectroscopy of damped Lyα systems:: The case of SBS 1543+593/HS 1543+5921

We report HST/STIS spectroscopy and Gemini/GMOS-N imaging of the Damped Ly alpha ( DLA) system toward HS 1543 + 5921 caused by the host star-forming galaxy (SFG) SBS 1543 + 593. The Gemini image shows new morphological details of this well-resolved DLA galaxy. In combination with previous optical spectra, the new UV spectra enable us to compare, for the first time, ionized and neutral gas-phase alpha-element abundances derived from emission- and absorption-line spectroscopy, in a bona fide DLA galaxy. The abundances we determine using emission- line diagnostics agree with those from absorption-line diagnostics. We present our results on a metallicity versus redshift diagram that combines local H (II) regions and SFGs with high-redshift DLAs, and discuss implications for the chemical evolution of galaxies.