AN ANALYTICAL MODEL OF THE LARGE NEUTRAL REGIONS DURING THE LATE STAGE OF REIONIZATION
Author(s)
Xu, Yidong; Yue, Bin; Su, Meng; Fan, Zuhui; Chen, Xuelei
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In this paper, we investigate the nature and distribution of large neutral regions during the late epoch of reionization. In the "bubble model" of reionization, the mass distribution of large ionized regions ("bubbles") during the early stage of reionization is obtained by using the excursion set model, where the ionization of a region corresponds to the first up-crossing of a barrier by random trajectories. We generalize this idea and develop a method to predict the distribution of large-scale neutral regions during the late stage of reionization, taking into account the ionizing background after the percolation of H II regions. The large-scale neutral regions, which we call "neutral islands," are not individual galaxies or minihalos, but larger regions where fewer galaxies formed and hence ionized later and they are identified in the excursion set model with the first down-crossings of the island barrier. Assuming that the consumption rate of ionizing background photons is proportional to the surface area of the neutral islands, we obtained the size distribution of the neutral islands. We also take the "bubbles-in-island" effect into account by considering the conditional probability of up-crossing a bubble barrier after down-crossing the island barrier. We find that this effect is very important. An additional barrier is set to avoid islands being percolated through. We find that there is a characteristic scale for the neutral islands, while the small islands are rapidly swallowed up by the ionizing background; this characteristic scale does not change much as the reionization proceeds.
Date issued
2014-02Department
Massachusetts Institute of Technology. Department of Physics; MIT Kavli Institute for Astrophysics and Space ResearchJournal
Astrophysical Journal
Publisher
Institute of Physics/American Astronomical Society
Citation
Xu, Yidong, Bin Yue, Meng Su, Zuhui Fan, and Xuelei Chen. “AN ANALYTICAL MODEL OF THE LARGE NEUTRAL REGIONS DURING THE LATE STAGE OF REIONIZATION.” The Astrophysical Journal 781, no. 2 (January 14, 2014): 97. © 2014 American Astronomical Society.
Version: Final published version
ISSN
0004-637X
1538-4357