The High-Redshift Quasar Luminosity Function from Multi-Epoch Imaging Surveys

Thesis (Ph.D.)--University of Washington, 2016-08Upcoming time-domain imaging surveys such as the LSST will detect over a million high-redshift z > 4 quasars, making complete spectroscopic followup unfeasible. Statistical estimates such as luminosity functions and clustering measurements will require purely photometric methods for classifying quasars, estimating redshifts and estimating selection functions. We validate these methods and constrain the optical, type I quasar luminosity function (QLF) at 3.75 3.75) and constraint on the characteristic luminosity (M* = −26.7) from a single, uniformly-selected survey at z ~ 4. We used the Sloan Digital Sky Survey (SDSS) repeated imaging of the 275 sq. deg. equatorial region of the sky (−50 3.4 with i 5. It predicts that quasars contribute 100% of the ionizing emissivity needed to balance hydrogen recombinations at z ~ 4. Given that at z ∼ 6 hydrogen recombines faster and quasars are less abundant, this result suggests that quasars contributed a negligible fraction of UV photons to H I reionization. Finally, we find that the number of quasars at z ~ 4 is sufficient to ionize He II by z ~ 3, consistent with independent observations of the He II Lyman-alpha forest and temperature of the intergalactic medium