First Results from SMAUG: The Need for Preventative Stellar Feedback and Improved Baryon Cycling in Semianalytic Models of Galaxy Formation
First Results from SMAUG: The Need for Preventative Stellar Feedback and Improved Baryon Cycling in Semianalytic Models of Galaxy Formation
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DOI：
10.3847/1538-4357/abc3c1
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发表时间：
2020-06
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通讯作者：
V. Pandya;R. Somerville;D. Angl'es-Alc'azar;C. Hayward;G. Bryan;D. Fielding;John C. Forbes;B. Burkhart;S. Genel;L. Hernquist;Chang-Goo Kim;S. Tonnesen;T. Starkenburg
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作者：
V. Pandya;R. Somerville;D. Angl'es-Alc'azar;C. Hayward;G. Bryan;D. Fielding;John C. Forbes;B. Burkhart;S. Genel;L. Hernquist;Chang-Goo Kim;S. Tonnesen;T. Starkenburg
半分析模型（SAMs）是追踪与星系形成相关的物理过程的一种很有前途的方法，但它们的许多近似值尚未经过严格测试。作为模拟多尺度天体物理学理解Galerkin项目的一部分，我们比较了FIRE-2流体动力学“放大”模拟的预测与圣克鲁斯SAM在相同的晕合并树上运行的预测，重点是全球质量流循环。我们的研究包括13个跨越低质量矮星（Mvir <$1010 M <$z = 0），中等质量矮星（Mvir <$1011 M <$）和银河系质量星系（Mvir <$1012 M <$）的晕。SAM和FIRE-2的预测在恒星和星际介质质量方面相对一致，但在环银河介质质量方面却有很大的不同（SAM比FIRE-2的矮星质量低103个数量级）。引人注目的是，SAM预测的矮星的气体吸积速率比FIRE-2高出10-100倍，这是SAM中更高的质量流出速率所补偿的。我们认为，最严重的模型差异是由于缺乏预防性的恒星反馈和假设晕气体冷却和回收SAM。作为解决这些模型紧张局势的第一步，我们提出了一个简单而有前途的新的预防性恒星反馈模型，其中超新星驱动的风所携带的能量被允许加热部分气体外的晕至少维里温度，吸积被抑制。
Semianalytic models (SAMs) are a promising means of tracking the physical processes associated with galaxy formation, but many of their approximations have not been rigorously tested. As part of the Simulating Multiscale Astrophysics to Understand Galaxies project, we compare predictions from the FIRE-2 hydrodynamical “zoom-in” simulations to those from the Santa Cruz SAM run on the same halo merger trees, with an emphasis on the global mass flow cycle. Our study includes 13 halos spanning low-mass dwarfs (Mvir ∼ 1010M⊙ at z = 0), intermediate-mass dwarfs (Mvir ∼ 1011M⊙), and Milky Way–mass galaxies (Mvir ∼ 1012M⊙). The SAM and FIRE-2 predictions agree relatively well with each other in terms of stellar and interstellar medium mass but differ dramatically on circumgalactic medium mass (the SAM is lower than FIRE-2 by ∼3 orders of magnitude for dwarfs). Strikingly, the SAM predicts higher gas accretion rates for dwarfs compared to FIRE-2 by factors of ∼10–100, and this is compensated for with higher mass outflow rates in the SAM. We argue that the most severe model discrepancies are caused by the lack of preventative stellar feedback and the assumptions for halo gas cooling and recycling in the SAM. As a first step toward resolving these model tensions, we present a simple yet promising new preventative stellar feedback model in which the energy carried by supernova-driven winds is allowed to heat some fraction of gas outside of halos to at least the virial temperature such that accretion is suppressed.