Simulated histories of reionization with merger tree of HII regions
  We describe a new methodology to analyze the reionization process in
numerical simulations: The evo- lution of the reionization is investigated by
focusing on the merger histories of individual HII regions. From the merger
tree of ionized patches, one can track the individual evolution of the regions
such as e.g. their size, or investigate the properties of the percolation
process by looking at the formation rate, the frequency of mergers and the
number of individual HII regions involved in the mergers. By applying this
technique to cosmological simulations with radiative transfer, we show how this
methodology is a good candidate to quantify the impact of the star formation
adopted on the history of the reionization. As an application we show how
different models of sources result in different evolutions and geometry of the
reionization even though they produce e.g. similar ionized fraction or optical
depth.
