The association between gas and galaxies II: The 2-point correlation function

We measure the 2-point correlation function, xi(AG), between galaxies and quasar absorption line systems at z1E17 cm^-2. For CIV absorbers, the peak strength of xi(AG) is comparable to that of HI absorbers with N(HI)>1E16.5 cm^-2. We do not reproduce the differences reported by Chen et al. between 1-D xi(AG) measurements using galaxy sub-samples of different spectral types, but the full impact of systematic differences in our samples is hard to quantify. We compare the observations with smoothed particle hydrodynamical (SPH) simulations and discover that in the observations xi(AG) is more concentrated to the smallest separations than in the simulations. The latter also display a `finger of god' elongation of xi(AG) along the LOS in redshift space, which is absent from our data, but similar to that found by Ryan-Weber for the cross-correlation of quasar absorbers and HI-emission-selected galaxies. The physical origin of these `fingers of god' is unclear and we highlight several possible areas for further investigation