The VLT/MUSE view of the central galaxy in Abell 2052. Ionized gas swept by the expanding radio source

TL;DR

This study uses VLT/MUSE observations to analyze how expanding radio lobes from the AGN in galaxy 3C317 displace and ionize the surrounding gas, revealing complex interactions and feedback mechanisms.

Contribution

First detailed integral field spectroscopic analysis of ionized gas filaments around the central galaxy in Abell 2052, highlighting the impact of radio lobes on multi-phase interstellar medium.

Findings

Dense gas up to 270 cm-3 in a quasi spherical outflow

Cavity expansion velocity estimated at 265 km/s

Ionization caused by shocks or cosmic rays, not AGN or star formation

Abstract

We report observations of the radio galaxy 3C317 (at z=0.0345) located at the center of the Abell cluster A2052, obtained with the VLT/MUSE integral field spectrograph. The Chandra images of this cluster show cavities in the X-ray emitting gas, which were produced by the expansion of the radio lobes inflated by the active galactic nucleus (AGN). Our exquisite MUSE data show with unprecedented detail the complex network of line emitting filaments enshrouding the northern X-ray cavity. We do not detect any emission lines from the southern cavity, with a luminosity asymmetry between the two regions higher than about 75. The emission lines produced by the warm phase of the interstellar medium (WIM) enable us to obtain unique information on the properties of the emitting gas. We find dense gas (up to 270 cm-3) that makes up part of a global quasi spherical outflow that is driven by the radio source, and obtain a direct estimate of the expansion velocity of the cavities (265 km s-1). The emission lines diagnostic rules out ionization from the AGN or from star-forming regions, suggesting instead ionization from slow shocks or from cosmic rays. The striking asymmetric line emission observed between the two cavities contrasts with the less pronounced differences between the north and south sides in the hot gas; this represents a significant new ingredient for our understanding of the process of the exchange of energy between the relativistic plasma and the external medium. We conclude that the expanding radio lobes displace the hot tenuous phase of the interstellar medium (ISM), but also impact the colder and denser ISM phases. These results show the effects of the AGN on its host and the importance of radio mode feedback.