The first generation of stars likely formed at redshifts as high as z>20.  In the absence of any feedback processes, these stars could form in abundance and they, and their accreting black hole (BH) remnants, could significantly ionize the intergalactic medium (IGM). The stellar-mass BH remnants could also grow into billion-solar mass BHs, as observed at redshift z=6.  However, the population of the first stars and BHs were likely self-regulating due to global feedback effects.  The low electron-scattering optical depth in the three-year WMAP data suggests that star-formation in the earliest halos was suppressed. I will discuss the photodissociation of H_2 molecules and other physical processes that could cause this suppression. The build-up of supermassive black holes was further hindered due to gravitational recoil, which removed coalescing BHs from the shallow potentials of high-redshift galaxies during their mergers.  The surviving BHs need to grow rapidly, at a modestly super-Eddington rate, to reach several billion solar masses by z=6.  I will also briefly discuss detecting the gravitational waves from high-redshift supermassive BH binaries by LISA, and the possibility of identifying electromagnetic counterparts to these LISA events.

Zoltan Haiman