Feedback from galaxy formation: Escaping ionizing radiation from galaxies at high redshift

Several observational and theoretical arguments suggest that starburst galaxies may rival quasars as sources of metagalactic ionizing radiation at redshifts z > 3. Reionization of the intergalactic medium (IGM) at z > 5 may arise, in part, from the first luminous massive stars. To be an important source of radiative feedback from star formation, a substantial fraction (similar to1%-10%) of the ionizing photons must escape the gas layers of the galaxies. Using models of smoothly distributed gas confined by dark matter (DM) potentials, we estimate the fraction, (f(esc)), of Lyman-continuum flux that escapes the halos of spherical galaxies as a function of their mass and virialization redshift. The gas density profile is found by solving the equation of hydrostatic equilibrium for the baryonic matter in the potential well of a DM halo with the density profile found by Navarro et al. We then perform a parametric study to understand the dependence of (f(esc)) on redshift, mass, baryonic fraction, star formation efficiency (SFE), stellar density distribution, and OB association luminosity function. We give useful analytical formulas for (f(esc)(z, M-DM)) Using the Press-Schechter formalism, we find that stellar reionization at z similar to 7 is probably dominated by small galactic subunits, with M-DM less than or similar to 10(7) M-circle dot and SFE similar to 10 times that in the Milky Way. This may affect the distribution of heavy elements throughout the intergalactic medium.