The Clustering of Galaxies around Three z ~ 3 Damped Lyα Absorbers

We present our results on the cross-correlation of Lyman break galaxies (LBGs) around three damped Lyα absorbers (DLAs) at z_abs ≃ 3 from deep [μ_I,AB(sky) ≃ 27.6 mag arcsec^-2] UBVI KPNO 4 m/MOSAIC images. The large area of the MOSAIC images, 0.31 deg² or ~65 × 65 h Mpc comoving at redshift z = 3, allows us to probe the clustering of LBGs on scales up to 20 Mpc comoving. Our survey covers a total of 1 deg² and contains ~3000 LBGs with photometric redshifts between 2.8 and 3.5. Using the redshift likelihood distributions with m_I as a prior, we selected LBGs within a redshift slice of width W_z = 0.15 (corresponding to σ_z, the uncertainty in photometric redshifts) centered on the redshift of the absorbers. Within that redshift slice, we find that the DLA-LBG cross-correlation w_dg is w_dg = (1.62 ± 1.32) × w_gg, where w_gg is the LBG autocorrelation. This corresponds to a correlation length of r₀ = 5 ± 4.5 h^-1 (comoving) (or r₀ = 7 ± 6.8 h Mpc). The cross-correlation is most significant on scales 5-10 Mpc. Through Monte Carlo simulations, we find that w_dg is significantly greater than zero at the greater than 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 w_dg/w_gg < 1 and w_dg/w_gg > 1, i.e., to test whether DLA halos are more or less massive than LBG halos.