Cosmic H II Regions: From the First Stars and Black Holes to the Present-day Universe

Marcelo Alvarez (Stanford)

At the end of the cosmic dark ages, the first stars and black holes created H II regions by their ionizing radiation. As more and more structure formed, these H II regions grew in abundance and size, eventually overlapping to reionize the universe by redshift z=6. I will first describe H II regions around the first stars, how the attendant photoionization heating changed their surroundings, and how their possible remnant black holes may have continued to emit ionizing radiation as they accreted. I will then describe current work on modelling the reionization process on larger scales, concentrating on the characteristic scales and topology of the H II regions. Finally, I will discuss the implications of our results for the properties of present-day galaxies.