Matt Kistler homepage. Matthew Kistler Determining the Escape Fraction of Ionizing Photons During Reionization with the GRB Derived Star-Formation Rate
How many ionizing photons escape their hosts?
The fraction of ionizing photons produced by stars that escape their host galaxies and can then ionize hydrogen in the surrounding intergalactic medium is a critical component in studying the era of reionization and early galaxy formation. Motivated by our first estimates of the star formation rate, in this paper, completed with Stuart Wyithe, Andrew Hopkins, Hasan Yuksel, and John Beacom, we attempt to break the degeneracy between the unknown values of the efficiency of high-redshift galaxies for converting gas into stars and the escape fraction of ionizing photons that typically plague reionization studies. Using a semi-analytic model for reionization, the GRB-derived star formation rate, and observations of the Ly-alpha forest and the CMB -- and assuming that UV photons from star-forming galaxies dominate the reionization process -- we show that the escape fraction of ionizing photons from high redshift galaxies is ~5%, a value stable against uncertainties in the implementation of radiative feedback, evolution of the escape fraction, and the IMF.
MNRAS version
