case western reserve university



Feedback in the Early Universe and X-ray reionization

Massimo Ricotti (The University of Maryland)

In this talk I will discuss galaxy feedback processes and their role in regulating the formation of the first sources of ionization. In recent years Population III stars have been a very popular candidate to explain the early reionization measured by WMAP. I will argue that they are probably unimportant for reionization and propose a different ionization scenario in which a prolonged partial ionization by X-rays emitted by accreting black holes precedes stellar reionization at z = 6. The X-ray reionization model can also be used to constrain the existence of Primordial Black holes more massive than 0.1-1 solar masses. The (preliminary) results are of interest in constraining the nature of the dark matter and MACHOs.