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

We use new observations of very weak CIV absorption lines associated with high-redshift Ly α absorption systems to measure the high-redshift Ly α line two-point correlation function (TPCF). These very weak CIV absorption lines trace small-scale velocity structure that cannot be resolved by Ly α absorption lines. We find that (1) high-redshift Ly α absorption systems with N(H I) > 3 × 10 cm are strongly clustered in redshift, (2) previous measurements of the Ly α 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 Ly α 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 ∼ 2− 3. We interpret these results as suggesting that many or most Ly α absorbers may arise in galaxies even at high redshifts, and, therefore, that the Ly α forest probes processes of galaxy formation and evolution for redshifts z ∼< 5. Subject headings: quasars: absorption lines, galaxies: evolution Instituto de F́ısica de Cantabria, Consejo Superior de Investigaciones Cient́ıficas – Universidad de Cantabria, Facultad de Ciencias, 39005 Santander, SPAIN. Departamento de F́ısica Moderna, Universidad de Cantabria, 39005 Santander, SPAIN. Astronomy Program, Department of Earth and Space Sciences, State University of New York at Stony Brook, Stony Brook, NY 11794–2100, U.S.A. Institute of Astronomy, University of Cambridge, Cambridge CB3 0HA, U.K. School of Physics, University of New South Wales, P.O. Box 1, Kensington, NSW, AUSTRALIA