运动学小尺度涨落不影响星系动力学质量的测量
Kinematical small-scale fluctuations do not affect the measurement of the dynamical mass of galaxies
AI总结：
本研究针对低质量星系小尺度运动学涨落是否影响动力学质量测量的问题，利用TNG50模拟样本验证，发现消除局域偏差后涨落与质量估算偏差几乎无关，证实小尺度运动学涨落不影响星系动力学质量测量。
摘要：
观测发现低质量星系的恒星运动学通常极不平滑，在小尺度上存在显著的运动学涨落，这与常用动力学模型得到的投影中心对称恒星运动学特征并不一致。本研究旨在检验这种高度运动学涨落是否会影响星系的动力学质量估算。我们采用星系恒星运动学的180度旋转自减得到的不对称参数η，来量化运动学小尺度涨落的程度。我们利用TNG50数值模拟构建了总质量已知的大样本模拟星系，随后得到了这些模拟星系的位力动力学质量估算量。我们发现，在对称假设下，模拟星系中心三维Re范围内的动力学质量整体平均精度约在0.1 dex以内，其中本文中的Re指投影圆化的恒星质量半半径。我们研究了不同η值的模拟星系的局部位力质量估算偏差。两个η分箱的最大偏差差约为0.16 dex，这一偏差与其他局域偏差相结合，或可助力将从大质量星系得到的观测位力质量估算量应用于其他类型的星系。我们发现，若适当地消除局域偏差，η与固有质量估算偏差的斯皮尔曼ρ系数接近于零。结果表明，即便对于低质量星系，高度运动学小尺度涨落的存在也不会影响星系动力学质量的测量。
英文摘要：
The stellar kinematics of low-mass galaxies are usually observed to be very unsmooth with significant kinematical fluctuations in small scales, which cannot be consistent with the projected centrosymmetric stellar kinematics obtained from commonly used dynamical models. In this work, we aim to test whether the high degree of kinematical fluctuations affects the dynamical mass estimate of galaxies. We use the asymmetry parameter $η$ obtained from the $180^{\circ}$ rotation self-subtraction of stellar kinematics of galaxies to quantify the degree of kinematical small-scale fluctuations. We use TNG50 numerical simulation to construct a large sample of mock galaxies with known total masses, and then obtained the virial dynamical mass estimator of these mock galaxies. We find that the dynamical masses within three-dimensional $R_{\rm e}$ to the mock galaxy centres are overall averagely accurate within around 0.1 dex under the symmetric assumption, while $R_{\rm e}$ means the projected circularized half-stellar mass radius in this work. We study the local virial mass estimation bias for mock galaxies of different $η$. The maximum bias difference of two $η$ bins is around 0.16 dex, which with other local biases may help apply the observational virial mass estimators obtained from massive galaxies to other types of galaxies. We find that the Spearman's $ρ$ of $η$ with the intrinsic mass estimation deviations is near zero if the local bias is eliminated properly. The results indicate that even for low-mass galaxies, the existence of high degree of kinematical small-scale fluctuations does not affect the measurement of the dynamical mass of galaxies.
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