Speaker
Description
In this talk, I will present a systematic study of how large‐scale environment influences the triggering and evolution of radio AGN. Using LOFAR observations at 144 MHz, we cross‐match a sample of more than 200.000 AGN from LoTSS DR2 with optical group and cluster catalogs to define subsamples of field, group and cluster AGN. A spectroscopic subset is also classified into HERGs and LERGs.
We find that, in the low‐power regime ($L_{144 \rm MHz} < 10^{22}$ W Hz$^{-1}$), field AGN dominate the population, indicating that high‐density halos might suppress the onset of low‐luminosity radio activity. Group and cluster AGN become significant only above this threshold.
At intermediate powers ($10^{22} In the high‐power regime ($L_{144 \rm MHz} > 10^{26}$ W Hz$^{-1}$), powerful HERGs are found exclusively in the field, implying that the most energetic radiative AGN activity is likely fueled only by mergers outside of dense halos. Radial distribution analysis shows that LERGs occupy the full extent of clusters, while they concentrate within $\sim$60 kpc from the centre of groups, consistent with jet‐mode feedback fueled by hot intra-group gas. HERGs are instead uniformly distributed out to $\sim$200 kpc in both groups and clusters, with cluster HERGs showing elevated densities at larger radii, which might be indicative of merger‐driven cold‐gas accretion. These findings support the hypothesis that hot gas in groups and clusters promotes kinetic, low‐efficiency modes, while cold‐gas availability in the field enables high‐efficiency radiative modes. We conclude that both halo mass and conditions of the local gas play a fundamental role in modulating AGN fueling and accretion and regulating feedback.
