The cross-correlation of damped Lyman-α systems and Lyman break galaxies

Abstract

We present the results from a survey for Lyman break galaxies (LBGs) associated with damped Lyman α systems (DLAs) at z ∼ 3 with the primary purpose of inferring the mass of DLAs from the DLA–LBG cross-correlation. We acquired imaging and spectroscopic data of nine quasar fields having 11 known z ∼ 3 DLAs over a total survey area of 465 arcmin 2. Using deep u′BVRI images, 796 LBG candidates with apparent magnitude 20 < R < 25.5 were photometrically selected from 17,343 sources detected in the field. Spectroscopic observations of 529 LBG candidates using the Keck Observatory yielded 339 redshifts. We conservatively identify 205 z > 2 LBGs and 6 z > 2 QSOs with 〈 z〉 = 3.02 ± 0.32 and present evidence of a spike of five LBGs associated with the z = 2.936 DLA in the PSS0808+5215 field. In addition, two of the discovered QSOs lie within Δ z ⩽ 0.015 of two of the DLAs. We compute the best fit correlation parameters of r 0 = 2.65 ± 0.5, γ = 1.55 ± 0.4 for the LBG auto-correlation and r 0 = 3.32 ± 1.3, γ = 1.74 ± 1.0 the DLA–LBG cross-correlation. Both values are consistent with the LBG auto-correlation values of [Adelberger, K.L., Steidel, C.C., Shapley, A.E., Pettini, M., 2003. ApJ 584, 45] within error. Finally, we introduce a one-degree deep survey underway to improve the DLA–LBG cross-correlation statistics and study the behavior of 3.5 < z < 5 systems on large scales.