Title

Feedback Processes During Reionization

Abstract

The first generation of stars are likely to have formed at very high
redshifts, z> 20, at locations corresponding to rare peaks of the
fluctuating primordial density field.  In the absence of any feedback
processes, these stars, and their accreting remnant black holes (BHs),
could significantly reionize the intergalactic medium (IGM).  However,
the population of the first stars and BHs were likely self-regulating
due to their global chemical, radiative, and thermodynamical impact on
the IGM, and reionization was delayed as a result.  I will argue that
star-formation was suppressed at high redshift in low-mass minihalos
by an early H_2 -dissociating background and that this suppression was
exacerbated by a prior photoionization heating of the IGM, and by the
strong clustering of the earliest ionizing sources.  The low electron
scattering optical depth in the three-year WMAP data offers empirical
support that the ionizing photon production in the earliest minihalos
was indeed suppressed.