Gas-phase metallicity break radii of star-forming galaxies in IllustrisTNG
Gas-phase metallicity break radii of star-forming galaxies in IllustrisTNG
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IllustrisTNG 中恒星形成星系的气相金属丰度断裂半径
DOI：
10.1093/mnras/stac3749
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发表时间：
2022
影响因子：
4.8
通讯作者：
Chen, Qian-Hui
中科院分区：
文献类型：
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作者：
Garcia, Alex M.;Torrey, Paul;Hemler, Z. S.;Hernquist, Lars;Kewley, Lisa J.;Nelson, Erica J.;Grasha, Kathryn;Zovaro, Henry R. M.;Chen, Qian-Hui
我们展示了TNG50-1恒星形成星系群在红移系数= 0-3处的径向气相金属丰度剖面、梯度和破裂半径。这些金属丰度剖面的特点是强调识别陡峭的内部梯度和平坦的外部梯度。由此，断裂半径Rbreak被定义为发生过渡的区域。我们观察到断裂半径随质量呈正趋势，随红移减弱。当用恒星半质量半径归一化时，断裂半径与质量和红移的关系较弱。为了测试我们的结果是否依赖于TNG50-1的分辨率或采用的物理特性，在TNG50-2和Illustris-1中进行了相同的分析。我们发现每个模拟的定性趋势大致一致；然而，TNG和Illustris所采用的物理特性不同，因此，按星系大小归一化的断裂会偏离约2个因子。为了理解断裂的来源，我们定义了两个相关的时间尺度：富集时间尺度和径向气体混合时间尺度。我们发现，在所有三次模拟运行中，当气体混合时间尺度是富集时间尺度的10倍时，会发生rbreak，并且具有一些弱的质量和红移依赖性。这意味着星系盘可以分为两部分：形成恒星的内盘具有陡峭的梯度，混合为主的外盘具有平坦的梯度，断裂半径标志着它们之间的过渡区域。
We present radial gas-phase metallicity profiles, gradients, and break radii at redshiftz= 0–3 from the TNG50-1 star-forming galaxy population. These metallicity profiles are characterized by an emphasis on identifying the steep inner gradient and flat outer gradient. From this, the break radius,Rbreak, is defined as the region where the transition occurs. We observe the break radius having a positive trend with mass that weakens with redshift. When normalized by the stellar half-mass radius, the break radius has a weaker relation with both mass and redshift. To test if our results are dependent on the resolution or adopted physics of TNG50-1, the same analysis is performed in TNG50-2 and Illustris-1. We find general agreement between each of the simulations in their qualitative trends; however, the adopted physics between TNG and Illustris differ and therefore the breaks, normalized by galaxy size, deviate by a factor of ∼2. In order to understand where the break comes from, we define two relevant time-scales: an enrichment time-scale and a radial gas mixing time-scale. We find thatRbreakoccurs where the gas mixing time-scale is ∼10 times as long as the enrichment time-scale in all three simulation runs, with some weak mass and redshift dependence. This implies that galactic discs can be thought of in two-parts: a star-forming inner disc with a steep gradient and a mixing-dominated outer disc with a flat gradient, with the break radius marking the region of transition between them.