The Galaxy Environment of O VI Absorption Systems

Abstract

We combine a FUSE sample of O VI absorbers (z<0.15) with a database of 1.07 million galaxy redshifts to explore the relationship between absorbers and galaxy environments. All 37 absorbers with N_OVI>=10^13.2 cm^-2 lie within 800 h^-1₇₀ kpc of the nearest galaxy, with no compelling evidence for O VI absorbers in voids. The O VI absorbers often appear to be associated with environments of individual galaxies. Gas with 10%+/-5% solar metallicity (O VI and C III) has a median spread in distance of 350-500 h^-1₇₀ kpc around L^* galaxies and 200-270 h^-1₇₀ kpc around 0.1L^* galaxies (ranges reflect uncertain metallicities of gas undetected in Lyα absorption). In order to match the O VI line frequency, (dN/dz)~20 for N_OVI>=10^13.2 cm^-2, galaxies with L<=0.1L^* must contribute to the cross section. Lyα absorbers with N_HI>=10^13.2 cm^-2 cover ~50% of the surface area of typical galaxy filaments. Two-thirds of these show O VI and/or C III absorption, corresponding to a 33%-50% covering factor at 0.1 Z_solar and suggesting that metals are spread to a maximum distance of 800 h^-1₇₀ kpc, within typical galaxy supercluster filaments. Approximately 50% of the O VI absorbers have associated Lyα line pairs with separations (Δv)_Lyα=50-200 km s^-1. These pairs could represent shocks at the speeds necessary to create copious O VI, located within 100 h^-1₇₀ kpc of the nearest galaxy and accounting for much of the two-point correlation function of low-z Lyα forest absorbers.