Hot Baryons and the Distribution of Metals in the Intergalactic Medium

Abstract

We use the observed number and column density distributions of intergalactic O VI absorbers to constrain the distribution of metals in the low-redshift intergalactic medium (IGM). In this simple model, the metals in the O VI absorbers are assumed to be produced in and propagated from low-redshift galaxies drawn from a real sample, in this case the Sloan Digital Sky Survey. This model can explain the observed d/dz of metals borne by O VI absorbers if these metals are dispersed out to ~200 kpc by galaxies down to L ~ L. Massive galaxies (L ~ L) by themselves cannot provide the metals unless they can enrich volumes out to 0.5-1 Mpc. This model suggests that the turnover in d/dN dz below log N(O ) 13.5 (Wλ = 50 mA) is likely a real effect resulting from the apparently limited volumes over which galaxies can disperse metals, rather than a consequence of survey incompleteness. If so, it would indicate that metals are not as widespread throughout the IGM, as they are assumed to be in cosmological simulations of the warm-hot IGM. Alternatively, our model estimates the fraction of O VI absorbers directly caused by galaxies, such as the known populations of highly ionized high-velocity clouds surrounding the Milky Way, rather than the hot IGM.