Photoionization, Numerical Resolution, and Galaxy Formation
Photoionization, Numerical Resolution, and Galaxy Formation
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光电离、数值分辨率和星系形成
DOI：
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发表时间：
1996
期刊：
影响因子：
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通讯作者：
N. Katz
中科院分区：
文献类型：
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作者：
D. Weinberg;L. Hernquist;N. Katz
利用结合了气体动力学和引力的宇宙学模拟，我们研究了紫外辐射背景光电离对星系形成的影响。在我们最高分辨率的模拟中，我们发现光电离对z = 2的星系的重子质量函数基本上没有影响，直到我们的分辨率极限~5 × 109 M。然而，我们发现模拟的质量分辨率与加热和冷却速率计算中包含的微观物理之间存在很强的相互作用。在低分辨率下，光致电离背景似乎可以抑制甚至相对大质量星系的形成。然而，当相同的初始条件下，质量分辨率提高了8倍，这种效果消失了。我们的结果表明，在解释结合流体力学和辐射物理学的宇宙学模拟结果时需要谨慎。例如，我们得出结论，有限分辨率的模拟可能会产生更准确的结果，如果它忽略了一些相关的物理过程，如光电离。在更高的分辨率下，模拟的大质量星系的人口是不敏感的光电离的治疗或列入星星形成的模拟，但它确实显着依赖于初始密度波动的幅度。到z = 2时，一个Ω = 1的冷暗物质模型已经形成了重子质量超过1011 M的星系。
Using cosmological simulations that incorporate gasdynamics and gravitational forces, we investigate the influence of photoionization by an ultraviolet radiation background on the formation of galaxies. In our highest resolution simulations, we find that photoionization has essentially no effect on the baryonic mass function of galaxies at z = 2, down to our resolution limit of ~5 × 109 M☉. We do, however, find a strong interplay between the mass resolution of a simulation and the microphysics included in the computation of heating and cooling rates. At low resolution, a photoionizing background can appear to suppress the formation of even relatively massive galaxies. However, when the same initial conditions are evolved with a factor of 8 improvement in mass resolution, this effect disappears. Our results demonstrate the need for care in interpreting the results of cosmological simulations that incorporate hydrodynamics and radiation physics. For example, we conclude that a simulation with limited resolution may yield more accurate results if it ignores some relevant physical processes, such as photoionization. At higher resolution, the simulated population of massive galaxies is insensitive to the treatment of photoionization or the inclusion of star formation in the simulations, but it does depend significantly on the amplitude of the initial density fluctuations. By z = 2, an Ω = 1 cold dark matter model normalized to produce the observed masses of present-day clusters has already formed galaxies with baryon masses exceeding 1011 M☉.