Probing the IGM–galaxy connection at z > 0.5 – II. New insights into the galaxy environments of O vi absorbers in PKS 0405−123

We present new absorption-line analysis and new galaxy survey data obtained for the field around PKS0405-123 at z=0.57. Combining previously known OVI absorbers with new identifications in the higher S/N UV spectra obtained with COS, we have established a sample of 7 OVI absorbers and 12 individual components at z=0.0918-0.495 along the sightline toward PKS0405-123. We complement the available UV absorption spectra with galaxy survey data that reach 100% completeness at projected distances rho0.04L* at rho0.3L* at rho13.6 and no detectable OVI absorption features. The Lya-only absorbers serve as a control sample in seeking the discriminating galactic features that result in the observed OVI absorbing gas at large galactic radii. We find a clear distinction in the radial profiles of mean galaxy surface brightness around different absorbers. Specifically, OVI absorbers are found to reside in regions of higher mean surface brightness at rho
Comment: 16 pages, 7 figures; accepted to Monthly Notices of the Royal Astronomical Society