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We examine the contribution of high-redshift (z>6) active galactic nuclei(AGNs) to cosmic hydrogen reionization, by tracing the growth and ionizingoutput of the first generation of supermassive black holes (SMBHs). Ourcalculations are anchored to the observed population of z~6 quasars, and traceback the evolving spectral energy distributions (SEDs) of the accretion flowsthat power these early AGNs and consider a variety of growth histories,including super-Eddington accretion. Compared to a fixed-shape SED, theevolving thin disks can produce ionizing radiation that is higher by up to~80%. Across a variety of SMBH growth scenarios, the contribution of AGNs toreionization is limited to late epochs (z<7), and remains sub-dominant comparedto star-forming galaxies. This conclusion holds irrespective of the (stillunknown) space density of low-luminosity z=6 AGNs, and for growth scenariosthat allow super-Eddington accretion. The contribution of AGNs to reionizationcan extend to earlier epochs (z>8) in scenarios with relative slow SMBH massgrowth, i.e., for low accretion rates and/or high spins. We finally demonstratethat our framework can reproduce the observed quasar proximity zone sizes, andthat compact proximity zones around z=6 quasars can be explained by the lateonset of super-Eddington accretion.

The Contribution of AGN Accretion Disks to Hydrogen Reionization