An Imaging and Spectroscopic Study of the z_abs=3.38639 Damped Lyα System in Q0201+1120: Clues to Star Formation at High Redshift

Abstract

We present the results of a series of imaging and spectroscopic observations aimed at identifying and studying the galaxy responsible for the z_abs=3.38639 damped Lyα system in the z_em=3.61 quasar Q0201+1120. We find that the damped Lyα systems (DLA) is part of a concentration of matter that includes at least four galaxies (probably many more) over linear comoving dimensions greater than 5 h^-1 Mpc. The absorber may be a 0.7L* galaxy at an impact parameter of 15 h^-1 kpc, but follow-up spectroscopy is still required for positive identification. The gas is turbulent, with many absorption components distributed over ~270 km s^-1 and a large spin temperature, T_s>~4000 K. The metallicity is relatively high for this redshift, Z_DLA~=1/20 Z_solar. From consideration of the relative ratios of elements that have different nucleosynthetic timescales, it would appear that the last major episode of star formation in this DLA occurred at z>~4.3, more than ~500 Myr prior to the time when we observe it. Based in large part on observations obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA and was made possible by the generous financial support of the W. M. Keck Foundation.