Probing the OVI forest

Recent FUSE and STIS observations of OVI absorption at low redshift along the sightline to distant quasars have been interpreted as the signature of a warm-hot diffuse component of the intergalactic medium (IGM). In these proceedings we show that the predicted numbers of such absorbers in numerical simulations agree with the observed characteristics, lending support to this idea. We find that collisionally ionized lines tend to be stronger and wider, while photo-ionized absorbers are weaker and narrower. We also find that a comparison of the predicted distribution of line widths to that observed is marginally too low.