ViCTORIA project: The LOFAR-MeerKAT view of AGN in Virgo cluster early-type galaxies

TL;DR

This study uses LOFAR and MeerKAT radio observations to analyze AGN activity in Virgo cluster early-type galaxies, revealing insights into their feedback mechanisms, duty cycle, and historical activity through low-frequency radio emissions.

Contribution

First detailed low-frequency radio survey of Virgo cluster early-type galaxies, linking radio luminosity with stellar mass and uncovering evidence of past AGN activity and feedback.

Findings

Detected 12 galaxies at 144 MHz, with 5 showing extended emission.

Radio luminosity correlates with host galaxy stellar mass.

Evidence of past AGN activity in NGC 4365 and NGC 4472.

Abstract

The evolution of Active Galactic Nuclei (AGN) is closely connected to their host galaxies and surroundings. Via feedback processes, AGN can counteract the cooling of the intracluster medium (ICM) and suppress star formation in their host galaxies. Radio observations at low frequencies provide a glimpse into the history of AGN activity. The Virgo cluster is a substantial reservoir of nearby galaxies and provides an ideal laboratory for the study of AGN as well as their feedback mechanisms. The aim of our work is to characterise the AGN population within the Virgo cluster down to low radio luminosities, constrain the AGN duty cycle and investigate environmental feedback in cluster member galaxies. We analyse 144 MHz and 1.3 GHz radio observations of early-type galaxies from the ACS Virgo Cluster Survey (ACSVCS) taken with LOFAR and MeerKAT. We detect 12 of these galaxies at 144 MHz, 5 of which show clearly extended radio emission. The radio luminosity shows a strong dependence on the stellar mass of the host galaxy, in agreement with previous results. As a notable outlier, the massive elliptical galaxy NGC 4365 ($M_* = 2.2 \times 10^{11} M_\odot$) is not detected as a compact source in the LOFAR observations. Instead, it is surrounded by diffuse, low-surface brightness emission, which hints towards a past phase of stronger nuclear activity. Furthermore, we find a cavity in NGC 4472 (= M 49) inflated by the wide-angle tail only visible in the LOFAR data, which implies that the cavity was created by a past outburst. The corresponding cavity power is of the same order of magnitude as the jet power in the present duty cycle of the AGN.