Astronomy and Astrophysics – Astrophysics
Scientific paper
2001-08-10
"The Physics of Galaxy Formation", ASP Conf. Ser. 222, Eds. M. Umemura and H. Susa (ASP: San Francisco), pp.109-114
Astronomy and Astrophysics
Astrophysics
A paper in "The Physics of Galaxy Formation", ASP Conf. Ser. 222, Eds. M. Umemura and H. Susa (ASP: San Francisco), pp.109-114
Scientific paper
Using 3D radiative transfer calculations on the reionization of an inhomogeneous universe, QSO absorption line systems are simulated and they are compared with observations of Ly$\alpha$ continuum depression at high redshifts. By this comparison, it is found that the metagalactic UV intensity decreases rapidly with $z$ at $z>4$ as $I_{21}=0.5\exp [3(4-z)]$, and the reionization must have taken place between $z=6$ and 10. Based on this time-dependence of UV background intensity, we explore the collapse of pregalactic clouds in the UV background, and find that the self-shielding is prominent above a mass scale as $ M_{BIF}=3.0\times 10^{11} M_\odot [(1+z_c)/5]^{-4.2}(I_{21}/0.5)^{0.6}. $ This mass scale predicts the bifurcation of galactic morphology, and by confrontation with observations it turns out that the bifurcation mass successfully discriminates between elliptical and spiral galaxies.
Nakamoto Taishi
Susa Hajime
Umemura Masayuki
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