GalICS 2.1：一个新的冷吸积、冷却、反馈及其在星系形成中作用的半解析模型
GalICS 2.1: a new semianalytic model for cold accretion, cooling, feedback and their roles in galaxy formation
摘要：
Dekel和Birnboim06提出，区分晚型和早型星系的质量尺度与稳定激波传播的临界晕质量有关，并表明他们可以重现所观察到的双峰尺度，以获得吸积气体金属丰度和激波半径的合理值。在这里，我们把他们的分析更进一步，提出了一个新的半解析模型，计算激波半径的第一原理。这一进步使我们能够单独计算每个光环的临界质量。分离冷模和热模吸积对最终星系质量的影响很小，如果反馈不优先耦合到热气体。我们还提出了一个改进的恒星反馈模型，其中70%的风质量是在一个寒冷的星系喷泉与较短的再吸积时间尺度在高质量。后者是使我们能够在整个红移范围0<z<2.5内再现星系质量函数的低质量端的关键机制。冷却必须缓和，以避免过度预测恒星质量大于1000亿太阳质量的星系的数量密度，但对于形成中等质量星系很重要。在维里质量大于3000亿太阳质量的情况下，冷吸积在高z时更为重要，气体从较小的立体角吸积，但在较低质量时情况并非如此，因为高z的细丝具有较低的金属丰度。我们的预测与观测到的星系际介质在0<z<5时的金属丰度演化是一致的。
英文摘要：
Dekel & Birnboim06 proposed that the mass-scale that separates late-type and early-type galaxies is linked to the critical halo mass for the propagation of a stable shock and showed that they could reproduce the observed bimodality scale for plausible values of the metallicity of the accreted gas and the shock radius. Here, we take their analysis one step further and present a new semianalytic model that computes the shock radius from first principles. This advancement allows us to compute the critical mass individually for each halo. Separating cold-mode and hot-mode accretion has little effect on the final galaxy masses if feedback does not preferentially couple to the hot gas. We also present an improved model for stellar feedback where 70% of the wind mass is in a cold galactic fountain with a shorter reaccretion timescale at high masses. The latter is the key mechanism that allows us to reproduce the low-mass end of the mass function of galaxies over the entire redshift range 0<z<2.5. Cooling must be mitigated to avoid overpredicting the number density of galaxies with stellar mass greater than a hundred billion Solar masses but is important to form intermediate-mass galaxies. At virial masses greater than three hundred billion Solar masses, cold accretion is more important at high z, where gas is accreted from smaller solid angles, but this is not true at lower masses because high-z filaments have lower metallicities. Our predictions are consistent with the observed metallicity evolution of the intergalactic medium at 0<z<5.
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