The Clustering of Galaxies around Three Z ∼ 3 Damped Ly-alpha Absorbers

We present out results on the cross-correlation of Lyman break galaxies (LBGs) around three damped Lyα absorbers (DLAs) at zabs ≃ 3 from deep (μI,AB(sky) ≃ 27.6mag arcsec) UBV I KPNO 4m/MOSAIC images. The large area of the MOSAIC images, 0.31 deg or ∼ 65 × 65h 71 Mpc co-moving at redshift z = 3, allows us to probe the clustering of LBGs on scales up to 20 Mpc co-moving. Our survey covers a total of 1 deg and contains ∼3,000 LBGs with photometric redshifts between 2.8 and 3.5. Using the redshift likelihood distributions with mI as a prior, we selected LBGs within a redshift slice of width Wz = 0.15 (corresponding to σz, the uncertainty in photometric redshifts) centered on the redshift of the absorbers. Within that redshift slice, we find that the DLA-LBG cross-correlation wdg is wdg = (1.62±1.32)×wgg , where wgg is the LBG auto-correlation. This corresponds to a correlation length of ro = 5 ± 4.5h (co-moving) (or ro = 7 ± 6.8h 71 Mpc). The cross-correlation is most significant on scales 5 − 10 Mpc. Through Monte Carlo simulations, we find that wdg is significantly greater than zero at the > 95% level. In three other redshift slices that do not contain a DLA, we do not find any evidence of clustering. A larger sample will enable us to discriminate between wdg/wgg < 1 or wdg/wgg > 1, i.e to test whether DLA halos are more or less massive than LBG halos. Subject headings: cosmology: observations — galaxies: evolution — galaxies: high-redshift — quasars: absorption lines — quasars: individual (APM08279+5255, PC1233+4752, J0124+0044)