Speaker
Dr
George Becker
(University of Cambridge)
Description
Reconciling our current constraints on hydrogen reionization with what we know about high-redshift galaxy populations points to interesting galaxy physics at early times. For example, in order to emit enough ionizing photons to complete reionization by z=6, it appears that faint sources must make a larger than expected contribution to the ionizing budget at z > 6, or else reionization galaxies must have different stellar populations and/or ionizing escape fractions than their lower-redshift counterparts. In this talk I will describe how careful measurements of the physical conditions in the IGM in the post-reionization epoch are providing unique insight into the properties of high-redshift galaxies. Specifically, new measurements of the ionizing UV background over 2 < z < 5 derived from measurements of the temperature and opacity of the IGM, combined with galaxy luminosity functions over the same redshift interval, are delivering new information on whether reionization at z > 6 is consistent with the ionizing emissivity of lower-redshift galaxies, and how the evolution in galaxy properties that enables reionization to occur continues to substantially lower redshifts.
