arXiv 2409.040172024-09astro-ph.GAastro-ph.CO

星系恒星性质对原初自旋因子的依赖性

Dependence of Galaxy Stellar Properties on the Primordial Spin Factor

Jun-Sung Moon, Jounghun Lee

备注：: Accepted for publication in JCAP, 8 figures, 3 tables, revised after referee's comments
发表信息：: JCAP03(2025)018

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AI总结：

本文利用TNG300-1模拟发现现今星系恒星性质仍显著依赖原初自旋因子τ，通过信息论方法分离出τ对尺寸、年龄、恒星形成率、颜色和金属丰度的净效应，并揭示恒星尺寸呈双峰伽马分布。

摘要：

我们给出了一项数值发现：现今星系的可观测恒星性质仍保留着对原初密度场和潮汐场的显著依赖。通过分析TNG300-1模拟中的星系目录，我们首先计算了原初自旋因子$τ$，其定义为在原星系位置处初始密度海森张量与势海森张量主轴之间错位程度的平均值。然后，我们在香农信息论框架下探究现今星系的六个恒星性质——即两个恒星尺寸（$R_{90\star}$和$R_{50\star}$）、年龄、比恒星形成率、光学颜色和金属丰度——是否以及在多大程度上与在$z=127$处测得的$τ$共享互信息。我们刻意控制TNG星系样本，使其在质量、环境密度和剪切分布上没有差异，从而分离出$τ$对每个星系恒星性质的净效应。在$M_{\star}/(h^{-1}\\,M_{\odot})\ge 10^{10}$的较高质量范围内，全部六个恒星性质都表现出与$τ$的显著互信息；而在$M_{\star}/(h^{-1}\\,M_{\odot})< 10^{10}$的较低质量范围内，六个性质中除比恒星形成率和颜色外的四个性质产生了显著的$τ$依赖信号。通过考察六个恒星性质的平均值如何随$τ$变化，我们还表明，源自具有较高$τ$值的原星系位置的星系往往具有更大的尺寸、更晚的形成时期、更高的比恒星形成率、更蓝的颜色和更低的金属丰度。研究还发现，星系恒星尺寸对$τ$的依赖最为稳健且与$M_{\star}$无关，其分布遵循双峰伽马分布，我们讨论了这一现象的物理含义。

英文摘要：

We present a numerical discovery that the observable stellar properties of present galaxies retain significant dependences on the primordial density and tidal fields. Analyzing the galaxy catalogs from the TNG300-1 simulations, we first compute the primordial spin factor, $τ$, defined as the mean degree of misalignments between the principal axes of the initial density and potential hessian tensors at the protogalactic sites. Then, we explore in the framework of Shannon's information theory if and how strongly each of six stellar properties of the present galaxies, namely two stellar sizes ($R_{90\star}$ and $R_{50\star}$), ages, specific star formation rates, optical colors and metallicities, share mutual information with $τ$, measured at $z=127$. Deliberately controlling the TNG galaxy samples to have no differences in the mass, environmental density and shear distributions, we single out net effects of $τ$ on each of the galaxy stellar properties. In the higher stellar mass range of $M_{\star}/(h^{-1}\,M_{\odot})\ge 10^{10}$, significant amounts of mutual information with $τ$ are exhibited by all of the six stellar properties, while in the lower range of $M_{\star}/(h^{-1}\,M_{\odot})< 10^{10}$ only four of the six properties except for the specific star formation rates and colors yield significant signals of $τ$-dependence. Examining how the mean values of the six stellar properties vary with $τ$, we also show that the galaxies originated from the protogalactic sites with higher $τ$ values tend to have larger sizes, later formation epochs, higher specific star formation rates, bluer colors and lower metallicities. It is also discovered that the galaxy stellar sizes, which turn out to be most robustly dependent on $τ$ regardless of $M_{\star}$, follow a bimodal Gamma distribution, the physical implication of which is discussed.

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