MAGIICAT VI。MgII组内介质在运动学上是复杂的
MAGIICAT VI. The MgII Intragroup Medium is Kinematically Complex
摘要：
通过比较星系群环境和孤立星系环星系介质中Mg Ⅱ的吸收，研究了环境对环星系介质的影响。如果有两个或两个以上的星系在吸收红移处，距离背景类星体的投影距离D=200 kpc，视线速度间隔为500 km/s，则MgII吸收体与一个群相关联。我们在$0.113<z_{\rm gal}<0.888$上编制了一个由74个星系（每组2-5个星系）组成的29组环境样本。组吸收体中值等效宽度（$\langle W_r(2796)\rangle=0.65\pm0.13$宽度）和覆盖分数（$f_c=0.89_{-0.09}^{+0.05}$）大于孤立吸收体（分别为$1.27σ$和$2.2σ$），但中值柱密度在统计学上一致。像素速度两点相关函数分析表明，组环境运动学在统计上与孤立环境（$0.8σ$）相当，但对于类似于流出运动学的高速分散体具有更大的功率。群吸收体在更大的速度下显示更大的光学深度。一个叠加模型，其中多个星系有助于观察到的气体匹配较大的等效宽度组吸收体，但过度预测的运动学显着，由于大的成员星系之间的速度分离。最后，星系-星系群（相似的成员星系光度）可能比星系-矮星系群（不同的光度）有更大的吸收体中值等效宽度（$1.7σ$）和速度色散（$2.5σ$）。我们认为，观察到的气体耦合到集团，而不是个别星系，形成一个群内介质。气体可能由多个星系通过外流风沉积到这个介质中，这些外流风在成员星系之间进行星系间转移，或者来自相互作用的成员的潮汐剥离。
英文摘要：
By comparing MgII absorption in the circumgalactic medium (CGM) of group environments to isolated galaxies, we investigated the impact of environment on the CGM. A MgII absorber is associated with a group if there are two or more galaxies at the absorption redshift within a projected distance of D=200 kpc from a background quasar and a line-of-sight velocity separation of 500 km/s. We compiled a sample of 29 group environments consisting of 74 galaxies (2-5 galaxies per group) at $0.113<z_{\rm gal}<0.888$. The group absorber median equivalent width ($\langle W_r(2796)\rangle=0.65\pm0.13$ Å) and covering fraction ($f_c=0.89_{-0.09}^{+0.05}$) are larger than isolated absorbers ($1.27σ$ and $2.2σ$, respectively) but median column densities are statistically consistent. A pixel-velocity two-point correlation function analysis shows that group environment kinematics are statistically comparable to isolated environments ($0.8σ$), but with more power for high velocity dispersions similar to outflow kinematics. Group absorbers display more optical depth at larger velocities. A superposition model in which multiple galaxies contribute to the observed gas matches larger equivalent width group absorbers, but overpredicts the kinematics significantly due to large velocity separations between member galaxies. Finally, galaxy--galaxy groups (similar member galaxy luminosities) may have larger absorber median equivalent widths ($1.7σ$) and velocity dispersions ($2.5σ$) than galaxy--dwarf groups (disparate luminosities). We suggest the observed gas is coupled to the group rather than individual galaxies, forming an intragroup medium. Gas may be deposited into this medium by multiple galaxies via outflowing winds undergoing an intergalactic transfer between member galaxies or from tidal stripping of interacting members.
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