Collapse of primordial clouds and the formation of a central core |
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Authors: | Toru Tsuribe Shu-Ichiro Inutsuka |
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Institution: | (1) Kyoto University, Kyoto 606-8502, Japan;(2) National Astronomical Observatory, Mitaka 181-8588, Japan |
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Abstract: | The collapse of rotating clouds is investigated using three-dimensional self-gravitating hydrodynamical simulations. We take
into account the detailed non-equilibrium chemical reactions for primordial gas that consists of pure hydrogen. The parameters
of the collapse and the condition of the fragmentation are compared with those of isothermal clouds. It is shown that the
geometrical flatness of the central region of the disc is a good indicator for predicting whether the clouds fragment or not.
If the flatness is greater than the critical value, ∼ 4π, a cloud fragments into filaments and blobs. On the other hand, if
the flatness is smaller than the critical value, fragmentation is not expected before the central core formation even if the
cooling is efficient and the total mass becomes much greater than the local Jeans mass at the centre. The critical mass is
found to be 3 × 106 M⊙ for a typical initial condition. If the initial cloud mass is smaller than this critical value, fragmentation before the
central core formation is not expected. For a typically estimated first collapsing cosmological baryonic object, M ≲ 106 M⊙, central core formation is expected and will have a significant effect on the later evolution of the whole system.
This revised version was published online in July 2006 with corrections to the Cover Date. |
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