On the possible environmental effect in distributing heavy elements beyond individual gaseous haloes

Abstract

We present a study of extended galaxy halo gas through HI and OVI absorption over two decades in projected distance at z ≈ 0.2. The study is based on a sample of 95 galaxies from a highly complete (> 80 per cent) survey of faint galaxies (L > 0.1L*) with archival quasar absorption spectra and 53 galaxies from the literature. A clear anticorrelation is found between HI (O VI) column density and virial radius normalized projected distance, d/Rh. Strong HI (O VI) absorption systems with column densities greater than 1014.0 (1013.5) cm-2 are found for 48 of 54 (36 of 42) galaxies at d Rh compared to isolated galaxies (κOVI ≈ 0.13 versus 0.04) but no excess HI absorption. These findings suggest that environmental effects play a role in distributing heavy elements beyond the enriched gaseous haloes of individual galaxies. Finally, we find that differential HI and OVI absorption between early- and late-type galaxies continues from d < Rh to d ≈ 3 Rh.