论文标题
椭圆星系恒星曲线的强大两参数描述
A robust two-parameter description of the stellar profile of elliptical galaxies
论文作者
论文摘要
恒星密度曲线通常用两个数字来汇总银河系：总恒星质量和半光半径。但是，由于光度观测的有限深度以及星系和弥漫性组内光线之间的区别，因此星系的总质量不是明确的数量。这限制了我们在模型和观察之间进行准确比较的能力。我希望以可以明确测量的数量来提供椭圆星系恒星密度分布的更强大的两参数描述。我建议在投影中使用10 kpc以内的恒星质量，$ m _ {*，10} $，以及同一孔径内的大量加权恒星密度斜率，$γ_ {*，10} $，为此目的。我使用Hyper Suprime-CAM调查的光度法，测量了$ M _ {*，10} $和$γ_ {*，10} $的分布。 $（M _ {*，10}，γ_ {*，10}）$的一对值可用于预测星系内10 kpc的恒星密度曲线，精度高于20％。同样，可以合并$ m _ {*，10} $和$γ_ {*，10} $，以获得恒星速度分散剂的代理，至少与恒星质量基本平面一样好。然后，我将观察到的$ M _ {*，10}-γ_{*，10} $的关系与Eagle参考模拟中类似选择的星系的关系进行了比较。观察和模拟的星系匹配$ M _ {*，10} = 10^{11} m_ \ odot $，但是Eagle $ m _ {*，10} -Camγ_ {*，10} $关系是较浅的，并且与观测值相比具有较大的内在散布。大规模椭圆星系恒星密度谱的新参数化提供了比较不同光度测量和流体动力学模拟的结果的更强大方法。
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.
