The He II Opacity of the Lyman-alpha Forest and the Intergalactic Medium

Abstract

Based on the empirical formulas governing the distribution of Ly-a forest absorption, we use a Monte-Carlo technique to calculate the average HeII optical depth produced by these forest lines. A substantial contribution to HeII absorption arises from extremely tenuous regions of intergalactic gas that are beyond the observational limits for HI absorption.

18 pages, including 4 figures To appear in A.J., February 1998

Cited by in corpus (9)

• The Lyman Alpha Forest in the Spectra of QSOs
• Resolving the Structure of Ionized Helium in the Intergalactic Medium with the Far Ultraviolet Spectroscopic Explorer
• A Study of the Reionization History of Intergalactic Helium with FUSE and VLT
• The Redshift Evolution of the Metagalactic Ionizing Flux Inferred from Metal Line Ratios in the Lyman Forest
• Mapping Low-Density Intergalactic Gas: a Third Helium Lyman-alpha Forest
• Spatial fluctuations in the spectral shape of the UV background at 2<z<3 and the reionization of helium
• Spectral energy distribution of the metagalactic ionizing radiation field from QSO absorption spectra
• Inhomogeneous metal enrichment at z \sim 1.9: the Lyman limit systems in the spectrum of the HDF-S quasar
• Statistical characteristics of observed Ly-$\alpha$ forest and the shape of initial power spectrum