Thermal and Dynamical Evolution of Primordial Gas Clouds : On the Formation of First Luminous Objects
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概要
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We investigate the thermal and dynamical evolution of primordial gas clouds in the universe after decoupling. Comparing the time scale of dynamical evolution with that of fragmentation, we can estimate the typical fragmentation scale. We propose the following scenario of the formation process of first luminous objects consisting of large number stars. First, by pancake collapse of the overdensity regions in the expanding universe or collision between clouds in potential wells, quasi-plane shocks form. If the shock-heated temperature is higher than about 10^4 K, the post-shock gas cools down to several hundred K by H_2 line cooling, and the shock-compressed layer fragments into filamentary clouds. The filamentary cloud collapses dynamically once more and fragments into cloud cores. Finally, a primordial star forms in a cloud core. We show that the minimum mass of the first star is essentially determined by the Chandrasekhar mass. Also, we investigate the dynamical collapse of cloud cores by numerical simulation and show that the evolution paths of the central regions of the cores depend only very weakly on the total core mass. After mass accretion, a massive star may be formed in a core, since the estimated mass accretion rate is very large. In such a case, it may be possible for many massive stars form almost simultaneously. Then the clouds can be luminous objects. On the other hand, if the shock-heated temperature is lower, effective star formation is delayed significantly.
- 理論物理学刊行会の論文
- 1998-11-25
著者
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須佐 元
立教大学理学部物理学科
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Yamada Masako
Department of Exercise Science and Physiology, School of Health Sciences, Prefectural University of
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Susa H
Center For Computational Physics University Of Tsukuba
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Yamada Masako
Department Of Physics Kyoto University
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NISHI Ryoichi
Department of Physics,Kyoto University
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SUSA Hajime
Center for Computational Physics,University of Tsukuba
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UEHARA Hideya
Division of Theoretical Astrophysics,National Astronomical Observatory
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OMUKAI Kazuyuki
Department of Physics ,Kyoto University
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Yamada Masako
Department Of Earth And Space Science Osaka University
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Uehara H
Department Of Physics Kyoto University
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Nishi R
Department Of Physics Niigata University
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Nishi Ryoichi
Department Of Physics Kyoto University
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Omukai K
National Astronomical Observatory Tokyo
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