AAS 197, January 2001
Session 20. Galaxy Formation and Chemical Evolution
Oral, Monday, January 8, 2001, 10:30am-12:00noon, San Diego

## [20.05] An Overdensity of Galaxies Near a Damped Lyman \alpha System at z=4

E. Gawiser, A. M. Wolfe (U.C. San Diego), J. X. Prochaska (Carnegie Observatory), K. M. Lanzetta (SUNY Stonybrook), A. Quirrenbach (U.C. San Diego)

We report the detection of galaxy clustering at z=4 from a systematic survey for Lyman break galaxies in a field containing a quasar with a foreground Damped Lyman \alpha system. Intriguingly, the overdensity of galaxies includes the Damped Lyman \alpha system. This provides a surprising indication that Damped Lyman \alpha systems may be highly biased and hence quite massive, although much better statistics are needed to test this possibility. We discuss how to obtain those statistics and illustrate the theoretical formalism needed to test galaxy formation using studies of this sort.