SAMI初步研究：Abell 85、Abell 168和Abell 2399的运动形态-密度关系
The SAMI Pilot Survey: The Kinematic Morphology-Density Relation in Abell 85, Abell 168 and Abell 2399
摘要：
本文研究了Abell 85、168和2399三个星系团中早型星系的运动学形态。利用悉尼-AAO多目标积分场光谱仪（SAMI）的数据，我们测量了这些集群中79个ETG的空间分辨运动学。我们计算$λ_{R}$，一个代理的投影特定的恒星角动量，为每个星系和分类的79 ETG在我们的样本为快速或慢速旋转。我们计算了Abell 85，168和2399的ETG种群中慢旋转子的分数（$f_{SR}$）分别为$0.21\pm0.08$，$0.08\pm0.08$和$0.12\pm0.06$，总分数为$0.15\pm0.04$。这些数字与文献中发现的值大致一致，证实了最近的工作，即ETG种群中慢转子的比例在全球环境中的许多数量级上是恒定的。我们研究的运动学类在每个集群中的分布作为环境的函数，使用投影密度的星系：运动形态密度关系。我们发现，在Abell 85中，$f_{SR}$在较高密度区域增加，但在Abell 168和Abell 2399中没有看到这种趋势。我们研究单个集群之间的差异来解释这一点。此外，我们发现在研究的两个集群，阿贝尔85和2399的郊区的慢旋转。这些星系居住在中低密度区域，显然不是在星系团环境的中心形成的。我们假设它们形成于群体的中心，并且第一次落入集群。
英文摘要：
We examine the kinematic morphology of early-type galaxies (ETGs) in three galaxy clusters Abell 85, 168 and 2399. Using data from the Sydney-AAO Multi-object Integral field spectrograph (SAMI) we measured spatially-resolved kinematics for 79 ETGs in these clusters. We calculate $λ_{R}$, a proxy for the projected specific stellar angular momentum, for each galaxy and classify the 79 ETGs in our samples as fast or slow rotators. We calculate the fraction of slow rotators in the ETG populations ($f_{SR}$) of the clusters to be $0.21\pm0.08$, $0.08\pm0.08$ and $0.12\pm0.06$ for Abell 85, 168 and 2399 respectively, with an overall fraction of $0.15\pm0.04$. These numbers are broadly consistent with the values found in the literature, confirming recent work asserting that the fraction of slow rotators in the ETG population is constant across many orders of magnitude in global environment. We examine the distribution of kinematic classes in each cluster as a function of environment using the projected density of galaxies: the kinematic morphology-density relation. We find that in Abell 85 $f_{SR}$ increases in higher density regions but in Abell 168 and Abell 2399 this trend is not seen. We examine the differences between the individual clusters to explain this. In addition, we find slow rotators on the outskirts of two of the clusters studied, Abell 85 and 2399. These galaxies reside in intermediate to low density regions and have clearly not formed at the centre of a cluster environment. We hypothesise that they formed at the centres of groups and are falling into the clusters for the first time.
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