期刊
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
卷 404, 期 4, 页码 2151-2169出版社
WILEY-BLACKWELL
DOI: 10.1111/j.1365-2966.2010.16433.x
关键词
stars: formation; galaxies: evolution; galaxies: formation; galaxies: kinematics and dynamics; galaxies: spiral
资金
- ISF [GIF I-895-207.7/2005]
- DIP
- France-Israel Teamwork in Sciences
- Einstein Center at HU
- NASA ATP [NAG5-8218]
We analyse the first cosmological simulations that recover the fragmentation of high-redshift galactic discs driven by cold streams. The fragmentation is recovered owing to an AMR resolution better than 70 pc with cooling below 104 K. We study three typical star-forming galaxies in haloes of similar to 5 x 1011 M(circle dot) at z similar or equal to 2.3 when they were not undergoing a major merger. The steady gas supply by cold streams leads to gravitationally unstable, turbulent discs, which fragment into giant clumps and transient features on a dynamical time-scale. The disc clumps are not associated with dark-matter haloes. The clumpy discs are self-regulated by gravity in a marginally unstable state. Clump migration and angular-momentum transfer on an orbital time-scale help the growth of a central bulge with a mass comparable to the disc. The continuous gas input keeps the system of clumpy disc and bulge in a near steady state for several Gyr. The average star formation rate, much of which occurs in the clumps, follows the gas accretion rate of similar to 45 M(circle dot) yr-1. The simulated galaxies resemble in many ways the observed star-forming galaxies at high redshift. Their properties are consistent with the simple theoretical framework presented in Dekel, Sari & Ceverino. In particular, a two-component analysis reveals that the simulated discs are indeed marginally unstable, and the time evolution confirms the robustness of the clumpy configuration in a cosmological steady state. By z similar to 1, the simulated systems are stabilized by a dominant stellar spheroid, demonstrating the process of 'morphological quenching' of star formation. We demonstrate that the disc fragmentation is not a numerical artefact once the Jeans length is kept larger than nearly seven resolution elements, i.e. beyond the standard Truelove criterion.
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