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.
Comment: Proceeding SF2A 2012, 5 pages, 4 figures