The interaction of 3C 401 with the surrounding intracluster medium

Abstract

We present an observation of the radio galaxy 3C 401 and the surrounding intracluster medium (ICM) of its host galaxy cluster by the Chandra X-ray Observatory. This luminous radio galaxy is notable in that it has characteristics intermediate between the Fanaroff-Riley type I and II morphologies. We clearly detect point-like emission coincident with the radio core of 3C 401, although the spatial resolution of even Chandra is only 2 kpc at the distance of 3C 401 (z = 0.201) and so the possibility remains that this is a dense (and rapidly cooling) thermal gaseous core in the centre of the ICM atmosphere. Strong departures from spherical symmetry in the central 10-20 kpc of the ICM clearly suggest interaction between the ICM and the radio lobes of 3C 401. A central X-ray bar probably results from the evacuation of two ICM cavities by the expanding radio lobes. Beyond these central regions, the cluster possesses a flatter profile than many clusters of comparable mass, suggesting the importance of ICM heating and entropy injection by 3C 401. We detect an interesting cross-like structure in the ICM on 100 kpc scales. We speculate that this could be a radio-galaxy-induced disturbance corresponding to a time when 3C 401 was substantially more powerful. A particularly exciting possibility is that this cross-like structure corresponds to a large-scale global g-mode oscillation excited by a past outburst of 3C 401.