MeerKAT观测并揭示合并星系团A520内部及周围的延展射电辐射
Extended radio emission in and around the merging cluster A520 as seen by MeerKAT
- U.S. Naval Research Laboratory（美国海军研究实验室）
- National Radio Astronomy Observatory（国家射电天文台）
- South African Radio Astronomy Observatory（南非射电天文台）
- NASA/Goddard Space Flight Center（NASA/戈达德太空飞行中心）
- INAF - Istituto di Radioastronomia（意大利国家天体物理研究所射电天文研究所）
- Università di Roma Tor Vergata（罗马托维加塔大学）
- INFN, Sezione di Roma 2, Università di Roma Tor Vergata（意大利国家核物理研究所罗马第二分部，罗马托维加塔大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究利用MeerKAT观测合并星系团A520，揭示其射电晕、射电尾、射电 relic及射电桥等延展射电辐射特征，为研究合并星系团的宇宙射线再加速等物理机制提供了关键观测证据。
AI中文摘要：
我们呈现了MeerKAT在1.28 GHz频段对阿贝尔520（Abell 520）的深度观测结果，阿贝尔520是一个正处于合并过程中的星系团，是合并产生的各类现象的宝库。MeerKAT兼具高角分辨率和对延展射电辐射的灵敏度，使我们能够揭示该星系团巨型晕及其外围神秘特征的前所未有的细节。我们发现，主射电晕沿东北-西南合并轴方向被两个X射线激波前沿清晰界定；在垂直方向上，晕的翼部平滑延伸超过2 Mpc，且外围光谱变陡。我们在主西南弓形激波的上游探测到微弱射电辐射，跨该激波的辐射率跃变可用于约束此处的物理机制。我们发现一条射电尾延伸过东北激波，直至东北外围气体匮乏、高熵的“暗次团”，该尾与暗次团的射电/X射线亮度比高于主晕，表明宇宙射线的高效再加速。我们还在星系团维里半径之外发现两个外围射电 relic（射电 relic），以及一条微弱、长约2 Mpc、宽的射电桥，沿垂直于合并轴的方向连接暗次团与其中一个 relic。暗次团与射电桥的光谱斜率与主晕一致，该桥和两个 relic 可能由维里半径处另一个巨型合并产生的激波前沿所致。
英文摘要：
We present results from a deep MeerKAT 1.28 GHz observation of Abell 520, a galaxy cluster in the middle of a merger and a treasure trove of merger-generated phenomena. MeerKAT's combination of high angular resolution and sensitivity to extended radio emission lets us uncover unprecedented detail of the cluster's giant halo and puzzling features beyond the halo. We find that the main radio halo is sharply bounded along the direction of the NE-SW merger axis by the two X-ray shock fronts. In the perpendicular direction, the halo wings smoothly span over 2 Mpc, with the spectrum steepening in the outskirts. We detect faint radio emission upstream of the main (SW) bow shock; the emissivity jump across this shock can be used to constrain the physical mechanisms at work there. We discover a tail of radio emission extending past the NE shock to the gas-poor, high-entropy ``dark subcluster'' in the NE outskirts. The tail and subcluster have a higher radio/X-ray brightness ratio than the main halo's, suggesting efficient reacceleration of cosmic rays. We also discover two peripheral radio relics beyond the cluster virial radius, and a faint, $\sim2$ Mpc long, broad radio bridge connecting the dark subcluster to one of the relics along the direction perpendicular to the merger axis. The spectral slopes of the dark subcluster and the bridge are consistent with that of the main halo. This bridge and both relics may be caused by another giant merger-generated shock front at the virial radius.
