The strongest cool core in REXCESS: Missing X-ray cavities in RXC J2014.8-2430

Abstract

We present a multiwavelength study of RXC J2014.8-2430, the most extreme cool-core cluster in the Representative $XMM-Newton$ Cluster Structure Survey (REXCESS), using $Chandra$ X-ray, Southern Astrophysical Research (SOAR) Telescope, Atacama Large Millimeter/submillimeter Array (ALMA), Very Large Array (VLA), and Giant Metrewave Radio Telescope (GMRT) observations. While feedback from an active galactic nucleus (AGN) is thought to be the dominant mechanism by which a cooling flow is suppressed, the $Chandra$ imaging observations surprisingly do not reveal the bi-lateral X-ray cavities expected in the intracluster medium (ICM) of an extreme cool core hosting a powerful radio source. We discuss the limits on the presence of any radio bubbles associated with any undetected X-ray cavities. We place upper limits on any significant X-ray AGN in the brightest cluster galaxy, and show that the X-ray peak is offset from the central radio source, which exhibits a steep low frequency radio spectrum indicative of electron ageing. The SOAR data reveal an extended, luminous emission line source. From our narrowband H$\alpha$ imaging of the BCG, the central H$\alpha$ peak is coincident with the radio observations, yet offset from the X-ray peak, consistent with sloshing found previously in this cluster. ALMA observations reveal a large reservoir of molecular gas that traces the extended H$\alpha$ emission. We conclude either that the radio source and its cavities in the X-ray gas are nearly aligned along the line of sight, or that ram pressure induced by sloshing has significantly displaced the cool molecular gas feeding it, perhaps preempting the AGN feedback cycle. We argue that the sloshing near the core is likely subsonic, as expected, given the co-location of the H$\alpha$, CO(1-0), radio continuum, and stellar emission peaks and their proximity to the intact cool core seen in X-ray.