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We study the effect of H I ionizing photons escaping from high-redshift(high-z) galaxies have on the He II ionizing ultraviolet background (UVB)radiation. While these photons do not directly interact with He II ions, weshow that they play an important role, through radiative transport, inmodifying the shape of He II ionizing part of UVB spectrum. Within the observedrange of UV escape from galaxies, we show that the rapid increase in He IILyman alpha effective optical depth at z~2.7 can naturally be explained byradiative transport effects. Therefore, the relationship between a wellmeasured He II Lyman alpha effective optical depth and the redshift in thepost-He II reionization era can be used to place additional constraints on theredshift evolution of UV escape from high-z galaxies. Our study also suggeststhat the escape fraction of H I ionizing photons from galaxies has an importantrole in the fluctuations of the He II ionizing UVB.

He II optical depth and UV escape fraction of galaxies