The radio galaxy 1321+045 is a rare example of a young, compact steep-spectrum source located in the center of a z = 0.263 galaxy cluster. Using a combination of Chandra, VLBA, VLA, MERLIN, and IRAM 30 m observations, we investigate the conditions that have triggered this outburst. We find that the previously identified 5 kpc scale radio lobes are probably no longer powered by the active galactic nucleus, which seems to have launched a new ∼20 pc jet on a different axis, likely within the last few hundred years. We estimate the enthalpy of the lobes to be , only sufficient to balance cooling in the surrounding 16 kpc for ∼9 Myr. The properties of the cluster’s intracluster medium (ICM) are similar to those of rapidly cooling nearby clusters, with a low central entropy (8.6 keV cm² within 8 kpc), short central cooling time (390 Myr), and t _cool/t _ff and t _cool/t _eddy ratios indicative of thermal instability out to ∼45 kpc. Despite previous detection of Hα emission from the brightest cluster galaxy, our IRAM 30 m observations do not detect CO emission in either the (1–0) or (3–2) transitions. We place 3σ limits on the molecular gas mass of M _mol ≤ 7.7 10⁹ M _⊙ and ≤5.6 10⁹ M _⊙ from the two lines respectively. We find indications of a recent minor cluster merger that has left a ∼200 kpc tail of stripped gas in the ICM, and probably induced sloshing motions.

射电星系 1321+045 是位于z = 0.263 星系团中心的年轻、紧凑的陡光谱源的罕见例子。使用 Chandra、VLBA、VLA、MERLIN 和 IRAM 30 m 观测的组合，我们调查了触发这次爆发的条件。我们发现之前确定的 5 kpc 尺度射电瓣可能不再由活动星系核提供动力，它似乎在不同的轴上发射了一个新的~20 pc 喷流，可能是在过去的几百年里。我们估计叶瓣的焓为，仅足以平衡周围 16 kpc 的冷却约 9 Myr。该星团的星团内介质 (ICM) 的特性与快速冷却附近星团的特性相似，具有低中心熵 (8.6 keV cm²在 8 kpc 内），较短的中央冷却时间（390 Myr），以及t _cool / t _ff和t _cool / t _涡流比率表明热不稳定性达到 ~45 kpc。尽管先前检测到来自最亮星团星系的 H α发射，但我们的 IRAM 30 m 观测未在 (1-0) 或 (3-2) 跃迁中检测到 CO 发射。我们对M _mol ≤ 7.7 10 ⁹ M _⊙和 ≤5.6 10 ⁹ M _⊙的分子气体质量设置了 3 σ限制 分别来自两行。我们发现了最近一次小簇合并的迹象，它在 ICM 中留下了大约 200 kpc 的汽提气体尾部，并且可能引起了晃动。