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arXiv 2002.01940astro-ph.GA
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椭圆星系恒星轮廓的稳健双参数描述

A robust two-parameter description of the stellar profile of elliptical galaxies

Alessandro Sonnenfeld

备注：
13 pages, 13 figures, submitted to Astronomy & Astrophysics
发表信息：
A&A 641, A143 (2020)
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摘要：

一个星系的恒星密度分布通常用两个数字来概括：恒星总质量和半光半径。然而，星系的总质量并不是一个定义明确的量，这是由于测光观测的深度有限，以及星系和扩散的星系内光之间的区别的任意性。这限制了我们在模型和观测之间进行准确比较的能力。我希望提供一个更强大的双参数描述的恒星密度分布的椭圆星系，在数量上，可以明确测量。为此，我建议使用投影中10千秒差距以内的恒星质量$M_{*,10}$和同一孔径内的质量加权恒星密度斜率$Γ_{*,10}$。我测量了$M_{*,10}$和$Γ_{*,10}$中的椭圆星系样本的分布，这些椭圆星系来自斯隆数字巡天和星系和质量大会巡天，使用的是超级超级凸轮巡天的测光。利用这对$(M_{*,10},Γ_{*,10})$值可以预测星系内部10 kpc的恒星密度分布，精度优于20%。类似地，$M_{*,10}$和$Γ_{*,10}$可以结合起来，得到一个至少和恒星质量基本面一样好的恒星速度色散的代理。作为第一个应用程序，我然后比较了观察到的$M_{*,10}-Γ_{*,10}$椭圆星系的关系，在鹰参考模拟类似的选定的星系。观测到的星系和模拟的星系在$M_{*,10}=10^{11}M_\odot$匹配，但鹰$M_{*,10}-Γ_{*,10}$关系较浅，并有一个更大的内在散射相比，观测。这种新的参数化的大质量椭圆星系的恒星密度分布提供了一个更强大的方式来比较不同的光度测量和流体动力学模拟的结果。

英文摘要：

The stellar density profile a galaxy is typically summarised with two numbers: total stellar mass and half-light radius. The total mass of a galaxy, however, is not a well-defined quantity, due to the finite depth of photometric observations and the arbitrariness of the distinction between galaxy and diffuse intra-group light. This limits our ability to make accurate comparisons between models and observations. I wish to provide a more robust two-parameter description of the stellar density distribution of elliptical galaxies, in terms of quantities that can be measured unambiguously. I propose to use the stellar mass enclosed within 10 kpc in projection, $M_{*,10}$, and the mass-weighted stellar density slope within the same aperture, $Γ_{*,10}$, for this purpose. I measured the distribution in $M_{*,10}$ and $Γ_{*,10}$ of a sample of elliptical galaxies from the Sloan Digital Sky Survey and the Galaxy And Mass Assembly survey, using photometry from the Hyper Suprime-Cam survey. The pair of values of $(M_{*,10},Γ_{*,10})$ can be used to predict the stellar density profile in the inner 10 kpc of a galaxy with better than 20% accuracy. Similarly, $M_{*,10}$ and $Γ_{*,10}$ can be combined to obtain a proxy for stellar velocity dispersion at least as good as the stellar mass fundamental plane. As a first application, I then compared the observed $M_{*,10}-Γ_{*,10}$ relation of elliptical galaxies with that of similarly selected galaxies in the EAGLE Reference simulation. Observed and simulated galaxies match at $M_{*,10}=10^{11}M_\odot$, but the EAGLE $M_{*,10}-Γ_{*,10}$ relation is shallower and has a larger intrinsic scatter compared to observations. This new parameterisation of the stellar density profile of massive elliptical galaxies provides a more robust way of comparing results from different photometric surveys and from hydrodynamical simulations.

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