赫克托星系巡天：介于两者之间的星系——阿贝尔3667并合星系团中的下落星系
Hector Galaxy Survey: Falling in Between - Infalling Galaxies in the Midst of the Abell 3667 Merger
AI总结：
本研究基于赫克托星系巡天数据，探究阿贝尔3667并合星系团中的RPS现象，发现核心区域存在增强的RPS，其由沿邻近纤维下落的星系与并合湍流环境相互作用驱动。
AI中文摘要：
星系团并合是否会增强冲压压力剥离（ram pressure stripping，RPS）并加速成员星系演化仍是一个悬而未决的问题。本研究利用赫克托星系巡天（Hector Galaxy Survey）的空间分辨数据，对近邻并合星系团阿贝尔3667（Abell 3667，红移z≈0.0553）中的星系种群展开研究。我们定义了一个RPS样本，该样本由赫克托巡天选定的存在电离气体扰动（如不对称尾或截断盘）的星系，以及补充的、经光学认证但未被赫克托巡天覆盖的“水母星系”组成。该RPS样本的大部分（约71%，误差范围+10%/-7%；共28个中的20个）位于R₂₀₀范围内，此区域受并合的影响更大。大部分不对称星系（约73%，误差范围+14%/-8%；共15个中的11个），尤其是具有极端RPS特征的星系，集中在星系团内部（R≲0.6 R₂₀₀），沿两个示踪激波的射电 relic 之间的并合轴分布。这些中心不对称星系呈现两个空间和运动学群组：一个位于西北（NW）子团，处于其射电 relic 的下游、高速星系际介质（intracluster medium，ICM）整体运动区域，具有蓝移视线速度；另一个主要是红移种群，位于主星系团（MC）附近，该区域也存在湍流ICM。尽管这两个样本在投影上与主星系团核心和西北子结构相关，但它们的速度表明并未被这些结构束缚。星系尾的朝向可用于推断轨道历史：西北星系尾指向远离星系团中心的方向，且常与并合轴对齐，表明是并合驱动的剥离；而主星系团星系尾则无此明显模式。星系尾整体向西延伸，主星系团星系尾指向正西，西北星系尾向西北偏移，表明西北种群和主星系团种群源自两个不同的纤维吸积事件。综上，我们的结果表明阿贝尔3667核心区域存在增强的RPS，主要由沿邻近纤维下落的星系驱动，这些纤维与并合驱动的湍流环境相互作用。
英文摘要：
Whether cluster mergers enhance ram pressure stripping (RPS) and accelerate member galaxy evolution remains an open question. Here, we investigate galaxy populations in the nearby merging cluster Abell 3667 ($z\simeq0.0553$) using spatially resolved data from the Hector Galaxy Survey. We define an RPS sample combining Hector-selected galaxies with ionised gas disturbances (e.g., asymmetric tails or truncated disks) and supplementary, optically identified jellyfish galaxies lacking Hector data. Most of the RPS sample ($\sim 71^{+10}_{-7}\%$; 20/28) lies within $R_{200}$, where the merger impact is greater. Most asymmetric galaxies ($\sim 73^{+14}_{-8}\%$; 11/15), especially those with extreme RPS signatures, are concentrated in the inner cluster ($R \lesssim 0.6\, R_{200}$), along the merger axis between two shock-tracing radio relics. These central asymmetric galaxies show two spatial and kinematic groups: one at the North-West (NW) subcluster, downstream of its radio relic in a region of high-velocity intracluster medium (ICM) bulk motion, with blueshifted line-of-sight velocities; and a mostly redshifted population near the main cluster (MC), which also shows a turbulent ICM. Despite their projected association with the MC core and NW substructure, both samples' velocities indicate they are not bound to them. Tail orientations give insight into orbital histories: NW tails point away from the cluster centre and often align with the merger axis, suggesting merger-driven stripping, while MC tails show neither pattern clearly. Tails are broadly westward, with MC tails tracing due west and NW tails shifted northwest, pointing to two distinct filamentary accretion events for the NW and MC populations. Together, our results indicate enhanced RPS in the heart of A3667, driven mainly by infalling galaxies accreted along nearby filaments interacting with the merger-driven turbulent environment.
