Effects of Early Cosmic Reionization on the Substructure Problem in Galactic Halo.pdfVIP

Draft version February 2, 2008 A Preprint typeset using L T X style emulateapj v. 11/12/01 E EFFECTS OF EARLY COSMIC REIONIZATION ON THE SUBSTRUCTURE PROBLEM IN GALACTIC HALO Hajime Susa1 Department of Physics, Rikkyo University, Nishi-Ikebukuro, Toshimaku, Japan Masayuki Umemura2 Center for Computational Sciences, University of Tsukuba, Japan 1 susa@rikkyo.ac.jp 4 2 umemura@rccp.tsukuba.ac.jp 0 Draft version February 2, 2008 0 2 ABSTRACT n Recent observations on the cosmic microwave background by Wilkinson Microwave Anisotropy Probe u ( WMAP) strongly suggest that the reionization of the universe took place quite early (z ∼ 17). On the J other hand, it has been pointed out that the cold dark matter cosmology suffers from the substructure 2 problem that subgalactic halos are overproduced than the observed dwarf galaxies in the Local Group. 1 In this paper, as a potential mechanism to solve this problem, we consider the feedback effects of the early reionization on the formation of small-scale structures. For this purpose, we perform 3D radiation 1 hydrodynamic simulations with incorporating the radiative transfer for ionizing photons. As a result, v