Papers - SUSA Hajime
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Thermal Evolution of Primordial Gas Clouds - A clue to Galaxy Formation -
Hajime Susa
1997.3
Single Work
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Fragmentation of the primordial gas clouds and the lower limit on the mass of the first stars
Uehara H, Susa H, Nishi R, Yamada M, Nakamura T.
Astrophysical Journal 473 ( 2 PART II ) 1996.12
Joint Work
We discuss the fragmentation of primordial gas clouds in the universe after decoupling. Comparing the timescale of collapse with that of fragmentation, we obtain the typical mass of a fragment both numerically and analytically. We show that the estimated mass gives the minimum mass of a fragment that is formed from the primordial gas cloud and essentially determined by the Chandrasekhar mass....
DOI: 10.1086/310409
Other Link: http://orcid.org/0000-0002-3380-5302
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The fragment mass scale of the primordial gas clouds. I: Non-spherical pressure-free collapse
Susa H, Uehara H, Nishi R.
Progress of Theoretical Physics 96 ( 6 ) 1073 - 1086 1996.12
Joint Work
We investigate the thermal evolution of non-spherical primordial gas clouds of mass M = 106Modot. We study two cases: 1) prolate and oblate clouds without angular momentum, 2) initially spherical, oblate and prolate clouds with angular momentum. In the spherical case, the magnitude of the angular momentum is the key quantity which determines the fragment mass. The fragment mass is found to be M >~ 90Modot for 10-2 <~ λ <~ 1, where λ is the cosmological spin parameter. For an oblate shape of initial gas clouds, the angular momentum is almost never important. In the case of prolate clouds with some angular momentum, collapse proceeds in the same way as in the spherical case, and a bounce occurs to form a disk due to the angular momentum. In any case, the estimated `fragment mass' must be almost above 90Modot for primordial gas clouds with typical angular momentum and typical oblateness or prolateness....
DOI: 10.1143/PTP.96.1073
Other Link: http://orcid.org/0000-0002-3380-5302
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Probability Distribution of Primordial Angular Momentum and Formation of Massive Black Holes
Progress of Theoretical Physics 1994.11
Single Work
We consider the joint probability distribution function for the mass contrast and angular momentum of over-density regions on the protogalactic scale and investigate the formation of massive black holes at redshift z >~ 10. We estimate the growth rate of the angular momentum by the linear perturbation theory and the decay rate by the Compton drag and apply the Press-Schechter theory to obtain the formation rate of massive black holes, assuming the full reionization of the universe at z = zion >> 10. We find the correlation between the mass contrast and angular momentum vanishes in the linear theory. However, application of the Press-Schechter theory introduces a correlation between the mass contrast and angular momentum of bound objects. Using thus obtained probability distribution, we calculate the mass fraction of black holes with M ~ 106 - 108 Modot in the universe. We find that it crucially depends on the reionization epoch zion. Specifically, for the standard CDM power spectrum with the COBE normalization, the condition zion >~ 500 must be satisfied to reproduce the observed number density of QSOs....
DOI: 10.1143/ptp/92.5.961
Other Link: http://orcid.org/0000-0002-3380-5302
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A numerical study of galaxy formation and the large scale structure of the universe.
Evolution of the Universe and its Observational Quest 1994
Single Work
The authors investigate the structure formation of the universe with hydrodynamical simulations. The galaxy formation is treated as cells which satisfy a certain condition. They consider the effects of galactic bursts on forming galaxies and the structure of the IGM, the angular correlation function of galaxies, and the luminosity functions of X-ray clusters....
Other Link: http://orcid.org/0000-0002-3380-5302