The radio properties of the cD galaxy of Abell 2390

We present multifrequency, multi-epoch radio imaging of the complex radio source B2151+174 in the core of the cluster, Abell 2390 (z≃ 0.23). From new and literature data, we conclude that the Faranoff-Riley type II (FRII)-powerful radio source is the combination of a compact, core-dominated ‘medium-sized symmetric object’ (MSO) with a more extended, steeper spectrum mini-halo. B2151+174 is unusual in a number of important aspects. (i) It is one of the most compact and flat spectrum sources in a cluster core known; (ii) it shows a complex, compact twin-jet structure in a north-south orientation; (iii) the orientation of the jets is 45° misaligned with apparent structure (ionization cones and dust disc) of the host galaxy on larger scales. Since the twin-jet of the MSO has its northern half with an apparent ‘twist’, it might be that precession of the central supermassive black hole explains this misalignment. B2151+174 may be an example of the early stage (103–104 yr duration) of a ‘bubble’ being blown into the intracluster medium where the plasma has yet to expand.