Yidong Xu
National Astron. Obs., Chinese Academy Sciences (NAOC) (Beijing, Chine)
Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris
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| « The Large Neutral Regions during the Late Stage of Reionization » |
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Yidong Xu |
| The excursion set theory has been successfully developed to model the halo evolution across cosmic time, as well as the large ionized regions (“bubbles”) during the early stage of reionization. In this talk, we will generalize the excursion set models and discuss the nature and distribution of large neutral regions during the late epoch of reionization. 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. We explicitly take into account the ionizing background after the percolation of HII regions, and the “bubbles-in-island” effect which is found to be important. An additional barrier is set to avoid islands being percolated through by inside-bubbles. We obtain the size distribution of the neutral islands, and 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. |
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mercredi 24 juin 2015 - 11:00 Salle des séminaires Évry Schatzman, Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |