AAS 199th meeting, Washington, DC, January 2002
Session 18. High Velocity Clouds and The Intergalactic Medium
Display, Monday, January 7, 2002, 9:20am-6:30pm, Exhibit Hall

## [18.06] Probing the Intergalactic Medium with the OVI Forest

T. Fang (MIT ), Greg L. Bryan Collaboration

Recent STIS and FUSE observations have detected OVI absorption lines at low redshift that are not clearly associated with any galactic system. In this paper, we argue that these lines are due to metal enriched hot gas in the intergalactic medium. Using numerical simulations of a cosmological-constant dominated cosmology, combined with reasonable assumptions about the metallicity distribution, we show that the number density and internal characteristics of these lines are correctly predicted. We find that the OVI is primarily produced by collisional ionization from gas at a few times 105 K for lines with equivalent widths larger than 40 mA, while weaker lines can also be produced by photo-ionization. The absorption occurs in diffuse gas in filaments at moderate overdensity (\delta ~5-100).