Strong Clustering of High-Redshift Lyman-alpha Forest Absorption Systems

Abstract

We use new observations of very weak CIV absorption lines associated with high-redshift Lyman-alpha absorption systems to measure the high-redshift Lyman-alpha line two-point correlation function (TPCF). These very weak CIV absorption lines trace small-scale velocity structure that cannot be resolved by Lyman-alpha absorption lines. We find that (1) high-redshift Lyman-alpha absorption systems with N(HI) > 3.10^14 cm^{-2} are strongly clustered in redshift, (2) previous measurements of the Lyman-alpha line TPCF underestimated the actual clustering of the absorbers due to unresolved blending of overlapping velocity components, (3) the present observations are consistent with the hypothesis that clustering of Lyman-alpha absorption systems extends to lower column densities, but maybe with smaller amplitude in the correlation function, and (4) the observed clustering is broadly compatible with that expected for galaxies at z \sim 2-3. We interpret these results as suggesting that many or most Lyman-alpha absorbers may arise in galaxies even at high redshifts, and, therefore, that the Lyman-alpha forest probes processes of galaxy formation and evolution for redshifts \lesssim 5.