Towards a Direct Detection of Warm Gas in Galactic Haloes at Cosmological Distances

Abstract

Recent highly sensitive detections of line emission from extended gas in the local universe demonstrate the feasibility of detecting H$\alpha$ emitting galactic halos out to $z\sim 1$. We determine the form of the surface brightness vs. redshift dependence which takes into account UV background evolution. Successful detections will have a major impact on a wide range of fields, in particular, the source of ionization in QSO absorption systems.

5 pages, 1 ps figure, TeX, uses mn.tex, accepted for publication in MNRAS Letters

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• Ionizing Photons and EUV Excesses in Clusters of Galaxies
• Low Redshift QSO Lyman alpha Absorption Line Systems Associated with Galaxies
• MCMC determination of the cosmic UV background at $z\simeq 0$ from H$\alpha$ fluorescence