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arXiv 1707.05985astro-ph.COastro-ph.GA
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遥远X射线发光星系团流体力学质量和动力学质量的比较

Comparison of hydrostatic and dynamical masses of distant X-ray luminous galaxy clusters

G. Foëx, H. Böhringer, G. Chon

摘要:

这项工作的主要目标是比较三个动力学质量估计的X射线流体静力学值的结果,集中在中间红移$z\sim0.3$的大质量星系团。我们估计动力学质量与维里定理,金斯方程,焦散线方法,使用宽场VIMOS光谱。我们调查的颜色选择的作用和子结构的动态估计的影响。Jeans和焦散方法给出了一致的结果,而维里定理导致质量$\sim15\%$更大。金斯质量、焦散质量和维里质量分别大于流体静力学值的$\sim20\%$、$\sim30\%$和$\sim50\%$。$\gtrsim50\%$的大分散主要是由于两个离群值RXCJ 0014和RXCJ 1347;排除后者会增加$\sim10\%$的质量比,从而在$\gtrsim2σ$产生显著的质量分数偏倚。我们发现的动态-静水质量比和两个子结构指标之间的相关性,这表明在动态测量的偏见。蓝星系的速度色散比红序列星系的速度色散大$\sim15\%$(去除子结构后的$\sim25\%$);使用后者会导致动力学质量$\sim10\%-15\%$更小。丢弃星系部分的子结构会使质量减少$\sim15\%$ ;对于质量更大的星系团,由于子结构的水平更高,影响更大。在子结构分析之后,动态质量与流体静力学值完全一致,并且将平均比率周围的散射除以$\sim2$。

英文摘要:

The main goal of this work is to compare the results of three dynamical mass estimators to the X-ray hydrostatic values, focussing on massive galaxy clusters at intermediate redshifts $z\sim0.3$. We estimated dynamical masses with the virial theorem, the Jeans equation, and the caustic method using wide-field VIMOS spectroscopy. We investigated the role of colour selection and the impact of substructures on the dynamical estimators. The Jeans and caustic methods give consistent results, whereas the virial theorem leads to masses $\sim15\%$ larger. The Jeans, caustic, and virial masses are respectively $\sim20\%$, $\sim30\%$, and $\sim50\%$ larger than the hydrostatic values. Large scatters of $\gtrsim50\%$ are mainly due to the two outliers RXCJ0014 and RXCJ1347; excluding the latter increases the mass ratios by $\sim10\%$, giving a fractional mass bias significant at $\gtrsim2σ$. We found a correlation between the dynamical-to-hydrostatic mass ratio and two substructure indicators, suggesting a bias in the dynamical measurements. The velocity dispersions of blue galaxies are $\sim15\%$ ($\sim25\%$ after removing the substructures) larger than that of the red-sequence galaxies; using the latter leads to dynamical masses $\sim10\%-15\%$ smaller. Discarding the galaxies part of substructures reduces the masses by $\sim15\%$; the effect is larger for the more massive clusters, owing to a higher level of substructures. After the substructure analysis, the dynamical masses are in perfect agreement with the hydrostatic values and the scatters around the mean ratios are divided by $\sim2$.

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