# Sub-Eddington super-massive black hole activity in Fornax early type galaxies

## TL;DR

This study investigates low-level super-massive black hole activity in Fornax cluster early-type galaxies using X-ray observations, revealing a lower active fraction than in the field and suggesting environmental effects on gas funneling.

## Contribution

First detailed X-ray analysis of SMBH activity in Fornax early-type galaxies, comparing cluster environment effects with Virgo and field galaxies.

## Key findings

- Active fraction in Fornax is less than in the field.
- No significant difference between Fornax and Virgo active fractions.
- Galaxy-galaxy interactions may enhance gas removal in dense environments.

## Abstract

We characterize the incidence and intensity of low-level super-massive black hole activity within the Fornax cluster, through X-ray observations of the nuclei of 29 quiescent early-type galaxies. Using the \textit{Chandra X-ray Telescope}, we target 17 galaxies from the HST Fornax Cluster Survey, down to a uniform (3$\sigma$) limiting X-ray luminosity threshold of $5\cdot10^{38}$ergs$^{-1}$, which we combine with deeper, archival observations for an additional 12 galaxies. A nuclear X-ray point-source is detected in 11 out of 29 targets. After accounting for the low mass X-ray binary contamination to the nuclear X-ray signal, the X-ray active fraction is measured at $26.6\% \pm 9.6\%$. The results from this analysis are compared to similar investigations targeting quiescent early types in the Virgo cluster, as well as the field. After correcting for the different mass distributions, the measured Fornax active fraction is less than the field fraction, at more than 3$\sigma$, confirming that the funneling of gas to the nuclear regions of cluster members is inhibited compared to those galaxies in the field. At the same time, we find no statistically significant difference between Fornax and Virgo galaxies, with only marginal evidence for a lower active fraction in Fornax (1 $\sigma$); if real, owing to Fornax's higher galaxy number density, this could indicate that galaxy-galaxy interactions are more effective at gas removal than galaxy-gas effects.