The escape fraction of ionizing photons from galaxies is a crucial quantity controlling the cosmic ionizing background radiation and the reionization. Various estimates of this parameter can be obtained in the redshift range z = 0-6, either from direct observations or from the observed ionizing background intensities. We compare them homogeneously in terms of the observed flux density ratio of ionizing (~900 Å rest-frame) to non-ionizing ultraviolet (~1500 Å rest-frame) corrected for the intergalactic absorption. The escape fraction is found to increase by an order of magnitude, from a value less than 0.01 at z ≲1 to about 0.1 at z ≳ 4.
|Monthly Notices of the Royal Astronomical Society: Letters
|Published - 2006 9月
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