The Connection between Galaxies and Intergalactic Absorption Lines at Redshift 2 ≲ z ≲ 3

Absorption-line spectroscopy of 23 background QSOs and numerous backgroundgalaxies has let us measure the spatial distribution of metals and neutralhydrogen around 1044 UV-selected galaxies at redshifts 1.8260 km/s) and produces very strong absorption lines (N_CIV >> 10^14cm^-2) in the spectra of background objects. Absorption with an average columndensity of N_CIV ~ 10^14 cm^-2 extends to 80 kpc, a radius large enough toimply that most strong intergalactic CIV absorption is associated withstar-forming galaxies like those in our sample. We find that the galaxy-CIVcross-correlation length increases with CIV column density and is similar tothe galaxy-galaxy length (r_0 ~ 4 h^-1 Mpc) for N_CIV > 10^12.5 cm^-2.Distortions in the redshift-space galaxy-CIV correlation function on smallscales may imply that some of the CIV systems have large peculiar velocities.Four of the five detected OVI absorption systems in our sample lie within 400proper kpc of a known galaxy. Strong Lyman-a absorption is produced by theintergalactic gas within 1 h^-1 comoving Mpc of most galaxies, but for asignificant minority (~1/3) the absorption is weak or absent. We were unable toidentify any statistically significant differences between galaxies with weaknearby HI absorption and the rest, although galaxies with weak absorption mayhave higher star-formation rates. Galaxies near intergalactic CIV systemsappear to reside in relatively dense environments and to have distinctivespectral energy distributions that are characterized by blue colors and youngages. (abridged)Comment: 20 pages of emulateapj, to appear in the Ap