Stormy Weather in 3C 196.1: Nuclear Outbursts and Merger Events Shape the Environment of the Hybrid Radio Galaxy 3C 196.1

Abstract

We present a multiwavelength analysis based on archival radio, optical, and X-ray data of the complex radio source 3C 196.1, whose host is the brightest cluster galaxy of a z = 0.198 cluster. HST data show Hα+[N II] emission aligned with the jet 8.4 GHz radio emission. An Hα+[N II] filament coincides with the brightest X-ray emission, the northern hotspot. Analysis of the X-ray and radio images reveals cavities located at galactic and cluster scales. The galactic-scale cavity is almost devoid of 8.4 GHz radio emission and the southwestern Hα+[N II] emission is bounded (in projection) by this cavity. The outer cavity is cospatial with the peak of 147 MHz radio emission, and hence we interpret this depression in X-ray surface brightness as being caused by a buoyantly rising bubble originating from an active galactic nuclei outburst ∼280 Myr ago. A Chandra snapshot observation allowed us to constrain the physical parameters of the cluster, which has a cool core with a low central temperature ∼2.8 keV, low central entropy index ∼13 keV cm² and a short cooling time of ∼500 Myr, which is < 0.05 of the age of the universe at this redshift. By fitting jumps in the X-ray density, we found Mach numbers between 1.4 and 1.6, consistent with a shock origin. We also found compelling evidence of a past merger, indicated by a morphology reminiscent of gas sloshing in the X-ray residual image. Finally, we computed the pressures, enthalpies E _cav and jet powers P _jet associated with the cavities: E _cav ∼ 7 × 10⁵⁸ erg, P _jet ∼ 1.9 × 10⁴⁴ erg s^-1 for the inner cavity and E _cav ∼ 3 × 10⁶⁰ erg, P _jet ∼ 3.4 × 10⁴⁴ erg s^-1 for the outer cavity.