论文标题
$ z = 2 $的模拟大型星系的恒星化学丰度
The Stellar Chemical Abundances of Simulated Massive Galaxies at $z = 2$
论文作者
论文摘要
我们在Illustristng模拟中分析了$ z = 2 $的大规模星系（$ \ log m_ \ ast/m_ \ odot> 10.5 $）的恒星丰度，目的是指导对当前和未来观察的解释，尤其是从詹姆斯·韦伯（James Webb）太空望远镜进行解释。我们发现，星系的有效尺寸（$ r_e $）强烈影响丰度测量值：[mg/h]和[fe/h]均与$ r_e $抗相关，而相对丰度[mg/fe]略微增加了$ r_e $。 [mg/fe]跟踪的$α$增强量较弱地跟踪了星系的编队时间尺度，并且主要取决于$ r_e $。孔径效果很重要：测量1〜kpc之内的恒星丰度，而不是在$ r_e $之内，可能会产生很大的不同。这些结果都是由于几乎通用，急剧下降的恒星丰度曲线，并不能随星系的大小扩展 - 小星系显得富含金属富含金属，因为它们的恒星生活在丰度较高的轮廓的内部。该轮廓的斜率主要由气相丰度曲线设置，而不是通过出色的年龄梯度来实质性地修改。气相丰度曲线又取决于气体分数和恒星形成效率的强径向依赖性。我们开发了一个简单的模型来描述化学富集，在该化学富集中，星系的每个径向箱被视为一个独立的闭盒系统。该模型重现了模拟星系的气相丰度谱，但不需要恒星丰度的详细分布，可能需要气体和/或金属传输。
We analyze the stellar abundances of massive galaxies ($\log M_\ast/M_\odot>10.5$) at $z=2$ in the IllustrisTNG simulation with the goal of guiding the interpretation of current and future observations, particularly from the James Webb Space Telescope. We find that the effective size, $R_e$, of galaxies strongly affects the abundance measurements: both [Mg/H] and [Fe/H] are anti-correlated with $R_e$, while the relative abundance [Mg/Fe] slightly increases with $R_e$. The $α$ enhancement as tracked by [Mg/Fe] traces the formation timescale of a galaxy weakly, and mostly depends on $R_e$. Aperture effects are important: measuring the stellar abundances within 1~kpc instead of within $R_e$ can make a large difference. These results are all due to a nearly universal, steeply declining stellar abundance profile that does not scale with galaxy size -- small galaxies appear metal-rich because their stars live in the inner part of the profile where abundances are high. The slope of this profile is mostly set by the gas-phase abundance profile and not substantially modified by stellar age gradients. The gas-phase abundance profile, in turn, is determined by the strong radial dependence of the gas fraction and star formation efficiency. We develop a simple model to describe the chemical enrichment, in which each radial bin of a galaxy is treated as an independent closed-box system. This model reproduces the gas-phase abundance profile of simulated galaxies, but not the detailed distribution of their stellar abundances, for which gas and/or metal transport are likely needed.
