Probing the Intergalactic Medium with the OVI Forest

Abstract

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 10^5 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).

4 pages, 4 figures (1 color). Accepted for publication in ApJ Letters

References in corpus (6)

• FUSE Observations of Outflowing OVI in the Dwarf Starburst Galaxy NGC1705
• The Ionization and Metallicity of the Intervening O VI Absorber at z = 0.1212 in the Spectrum of H1821+643
• Revealing the Warm-Hot Intergalactic Medium with OVI Absorption
• The Statistical and Physical Properties of the Low Redshift Lyman Alpha Forest Observed with HST/STIS
• Chandra Observations of Two High-Redshift Quasars
• High-resolution O VI absorption line observations at 1.2 < z < 1.7 in the bright QSO HE 0515-4414

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