标题： 环境对群体规模光环形态和动力学的影响 显示英文标题

标题： Environmental Influences on the Morphology and Dynamics of Group Size Haloes

摘要： 我们使用基于“朋友引力”（FOF）算法识别的群组大小晕族，在一个符合标准的$\Lambda \rm{CDM}$GADGET2（纯暗物质）模拟中研究晕族属性对环境的依赖性，这些晕族位于$z=0$处。 这项研究利用了不同距离最近的大质量{\em 聚类}晕族的样本进行。 我们发现，具有亚结构的晕族比例在高密度区域通常会增加。 晕族的平均轴比$<c/a>$也在过密区域增加，这一事实适用于所有研究范围内的晕族质量。 这可以解释为高密度区域的晕族形成时间更早，因此有更多的时间演化并变得更接近球形。 此外，这一解释得到了以下事实的支持：在给定的晕族-团簇距离上，具有亚结构的晕族比没有亚结构且质量相同的晕族更加拉长，这反映了晕族的暴胀（因此球化）过程被合并事件所中断。 具有强烈亚结构的低质量晕族的速度弥散度，在靠近大质量团簇时相对于具有低水平亚结构或位于低密度环境中的等质量晕族，表现出显著增加。 从低密度到高密度区域，形状与速度椭球主轴之间的对齐信号逐渐减弱，而这种对齐对于没有亚结构的晕族更强。 我们也发现，与其他研究一致，晕族的主要轴倾向于对齐，次要轴大致垂直于晕族所在纤维的方向，在大质量团簇附近这种效应更为明显。 显示英文摘要

摘要： We use group size haloes identified with a ``friends of friends'' (FOF) algorithm in a concordance $\Lambda \rm{CDM}$ GADGET2 (dark matter only) simulation to investigate the dependence of halo properties on the environment at $z=0$. The study is carried out using samples of haloes at different distances from their nearest massive {\em cluster} halo. We find that the fraction of haloes with substructure typically increases in high density regions. The halo mean axial ratio $<c/a>$ also increases in overdense regions, a fact which is true for the whole range of halo mass studied. This can be explained as a reflection of an earlier halo formation time in high-density regions, which gives haloes more time to evolve and become more spherical. Moreover, this interpretation is supported by the fact that, at a given halo-cluster distance, haloes with substructure are more elongated than their equal mass counterparts with no substructure, reflecting that the virialization (and thus sphericalization) process is interrupted by merger events. The velocity dispersion of low mass haloes with strong substructure shows a significant increase near massive clusters with respect to equal mass haloes with low-levels of substructure or with haloes found in low-density environments. The alignment signal between the shape and the velocity ellipsoid principal axes decreases going from lower to higher density regions, while such an alignment is stronger for haloes without substructure. We also find, in agreement with other studies, a tendency of halo major axes to be aligned and of minor axes to lie roughly perpendicular with the orientation of the filament within which the halo is embedded, an effect which is stronger in the proximity of the massive clusters.