Buoyancy-driven inflow to a relic cold core: the gas belt in radio galaxy 3C 386

TL;DR

This study uses X-ray observations to analyze a gas belt around radio galaxy 3C 386, revealing a buoyancy-driven inflow of group gas towards the cold core, with implications for galaxy group dynamics.

Contribution

It introduces the concept of buoyancy-driven inflow in the context of radio galaxy gas belts, supported by X-ray measurements of temperature structure and gas dynamics.

Findings

Gas belt temperature is $0.94 ext{ keV}$, cooler than the surrounding atmosphere.

Temperature structure indicates inflow of gas towards the core.

Inverse-Compton emission suggests magnetic field below equipartition.

Abstract

We report measurements from an XMM-Newton observation of the low-excitation radio galaxy 3C 386. The study focusses on an X-ray-emitting gas belt, which lies between and orthogonal to the radio lobes of 3C 386 and has a mean temperature of $0.94\pm0.05$ keV, cooler than the extended group atmosphere. The gas in the belt shows temperature structure with material closer to the surrounding medium being hotter than gas closer to the host galaxy. We suggest that this gas belt involves a `buoyancy-driven inflow' of part of the group-gas atmosphere where the buoyant rise of the radio lobes through the ambient medium has directed an inflow towards the relic cold core of the group. Inverse-Compton emission from the radio lobes is detected at a level consistent with a slight suppression of the magnetic field below the equipartition value.