2011MNRAS.411.1641E

We report on a deep, multiwavelength study of the galaxy cluster MACS J1931.8-2634 using Chandra X-ray, Subaru optical and Very Large Array 1.4-GHz radio data. This cluster (z= 0.352) harbours one of the most X-ray luminous cool cores yet discovered, with an equivalent mass, cooling rate within the central {img} is ∼700 M_☉/yr. Unique features observed in the central core of MACS J1931.8-2634 hint to a wealth of past activity that has greatly disrupted the original cool core. The X-ray and optical data suggest oscillatory motion of the cool core along a roughly north-south direction. We also observe a spiral of relatively cool, dense, X-ray emitting gas connected to the cool core, as well as highly elongated intracluster light (ICL) surrounding the cD galaxy. For a cluster with such a high-nominal cooling rate, this cluster is missing the central metallicity peak almost always seen in the cool-core clusters, which suggest bulk transport of cool gas out to large distances from the centre. Extended radio emission is observed surrounding the central active galactic nucleus (AGN), elongated in the east-west direction, spatially coincident with X-ray cavities. The power input required to inflate these `bubbles' is estimated from both the X-ray and radio emission to reside between P_jet∼ 4-14 {x} 10⁴⁵ erg/s, putting it among the most powerful jets ever observed. This combination of a powerful AGN outburst and bulk motion of the cool core has resulted in two X-ray bright ridges to form to the north and south of the central AGN at a distance of approximately 25 kpc. The northern ridge has spectral characteristics typical of cool cores: it contains low-temperature high-density metal-rich gas and is consistent with being a remnant of the cool core after it was disrupted by the AGN and bulk motions. It is also the site of Hα filaments and young stars. The X-ray spectroscopic cooling rate associated with this ridge is ∼165 M_☉/yr, which agrees with the estimate of the star formation rate from broad-band optical imaging (∼170 M_☉/yr). MACS J1931.8-2634 appears to harbour one of the most profoundly disrupted low-entropy cores observed in a cluster, and offers new insights into the survivability of cool cores in the context of hierarchical structure formation.