# On the slow quenching of M* galaxies: heavily-obscured AGNs clarify the picture

## TL;DR

This study explores how heavily-obscured X-ray AGNs in $ ext{M}^ ext{star}$ galaxies provide insights into the slow quenching process, suggesting mergers after quenching onset rather than as its cause.

## Contribution

It reveals that heavily-obscured X-ray AGNs are mainly in the process of quenching $ ext{M}^ ext{star}$ galaxies, supporting a merger-driven slow quenching scenario.

## Key findings

- Radio-loud AGNs are in already-quenched, very massive galaxies.
- Heavily-obscured X-ray AGNs are in $ ext{M}^ ext{star}$ galaxies undergoing quenching.
- Mergers are likely aftermath, not cause, of quenching.

## Abstract

We investigate the connection between X-ray and radio-loud AGNs and the physical properties of their evolved and massive host galaxies, focussing on the mass-related quenching channel followed by $\mathcal{M}^\star (\simeq 10^{10.6} M_\odot)$ galaxies in the rest-frame NUVrK colour diagram at $0.2 < z < 0.5$. While our results confirm that (1) radio-loud AGNs are predominantly hosted by already-quenched and very massive ($M_*>10^{11}M_\odot$) galaxies, ruling out their feedback as a primary driver of $\mathcal{M}^\star$ galaxy quenching, we found that (2) X-ray AGNs affected by heavy obscuration of their soft X-ray emission are mostly hosted by $\mathcal{M}^\star$ galaxies that are in the process of quenching. This is consistent with a quenching scenario that involves mergers of (gas-poor) $\mathcal{M}^\star$ galaxies $after$ the onset of the quenching process, i.e., a scenario where $\mathcal{M}^\star$ galaxy mergers are not the cause but rather an aftermath of the quenching mechanism(s). In that respect, we discuss how our results may support a picture where the slow quenching of $\mathcal{M}^\star$ galaxies happens due to halo-halo mergers along cosmic filaments.