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arXiv 2212.03255astro-ph.GAastro-ph.CO
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THESAN-HR:再电离如何影响早期星系演化?

THESAN-HR: How does reionization impact early galaxy evolution?

Josh Borrow, Rahul Kannan, Enrico Garaldi, Aaron Smith, Mark Vogelsberger, Rüdiger Pakmor, Volker Springel, Lars Hernquist

AI总结:

本文提出分辨率提高50倍的THESAN-HR辐射流体动力学模拟,自洽考察再电离对早期星系的反作用,并表明非均匀UV背景对准确预测低质量晕星系性质至关重要。

摘要:

早期星系是再电离的辐射源,而再电离过程产生的光加热反馈预计会降低低质量晕中的恒星形成效率。因此,为了全面理解再电离与星系形成,我们必须研究它们彼此之间的影响。迄今为止,THESAN项目一直旨在研究星系形成物理对再电离的影响,但在这里,我们提出分辨率提高50倍($m_{\rm b} \approx 10^4$ M$_\odot$)的新THESAN模拟,旨在自洽地研究再电离对星系的反作用。通过分辨维里温度$T_{\rm vir} < 10^4$ K的晕,我们能够证明,简单的、空间均匀的再电离模型不足以研究早期星系演化。将自洽的THESAN模型(采用完全耦合的辐射流体动力学)与均匀UV背景进行比较,我们能够表明,到$z=5$时,THESAN中预测的星系在物理尺度上更大(约2倍)、金属富集程度更低(约0.2 dex),并且数量更少(在$M_{\rm 1500}=-10$时约少10倍)。我们表明,恒星形成和富集模式的差异会导致对低质量晕中的恒星形成、低金属度恒星形成,甚至晕的占据比例产生显著不同的预测。我们认为,旨在研究$z \gtrsim 3$早期星系形成的宇宙学星系形成模拟必须采用空间非均匀的UV背景,才能准确再现星系性质。

英文摘要:

Early galaxies were the radiation source for reionization, with the photoheating feedback from the reionization process expected to reduce the efficiency of star formation in low mass haloes. Hence, to fully understand reionization and galaxy formation, we must study their impact on each other. The THESAN project has so far aimed to study the impact of galaxy formation physics on reionization, but here we present the new THESAN simulations with a factor 50 higher resolution ($m_{\rm b} \approx 10^4$~M$_\odot$) that aim to self-consistently study the back-reaction of reionization on galaxies. By resolving haloes with virial temperatures $T_{\rm vir} < 10^4$~K, we are able to demonstrate that simplistic, spatially-uniform, reionization models are not sufficient to study early galaxy evolution. Comparing the self-consistent THESAN model (employing fully coupled radiation hydrodynamics) to a uniform UV background, we are able to show that galaxies in THESAN are predicted to be larger in physical extent (by a factor $\sim 2$), less metal enriched (by $\sim 0.2$~dex), and less abundant (by a factor $\sim 10$ at $M_{\rm 1500}~=~-10$) by $z=5$. We show that differences in star formation and enrichment patterns lead to significantly different predictions for star formation in low mass haloes, low-metallicity star formation, and even the occupation fraction of haloes. We posit that cosmological galaxy formation simulations aiming to study early galaxy formation $z \gtrsim 3$ must employ a spatially inhomogeneous UV background to accurately reproduce galaxy properties.

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