The warm-hot intergalactic medium at $\mathsf{\vec {z}\sim2.2}$: Metal enrichment and ionization source

Abstract

Results are presented for our search for warm-hot gas towards the quasar Q 0329-385. We identify ten O vi systems of which two are within 5000 km s-1 of zem and a third one should be of intrinsic origin. The seven remaining systems have H i column densities cm-2. At least ~1/3 of the individual O vi sub-systems have temperatures K and cannot originate in collisionally ionized gas. Photoionization by a hard UV background field reproduces well the ionic ratios for metallicities in the range solar, with possibly sub-solar N/C relative abundance. For , the sizes inferred for the O vi clouds are in some cases larger than the maximum extent implied by the Hubble flow. This constraint is fulfilled assuming a moderate overabundance of oxygen relative to carbon. For a soft UV ionizing spectrum, an overabundance of O/C is required, . For a hard(soft) U spectrum and , the O vi regions have overdensities .