On the slow quenching of ℳ* galaxies: heavily obscured AGNs clarify the picture
Abstract
We investigate the connection between X-ray and radio-loud active galactic nuclei (AGNs) and the physical properties of their evolved and massive host galaxies, focussing on the mass-related quenching channel followed by $\mathcal {M}^\star (\simeq 10^{10.6} \, \mathrm{M}_\odot)$ galaxies in the rest-frame NUV-r versus r-K (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 ( $M_*\gt 10^{11}\, \mathrm{M}_\odot$ ) 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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- July 2020
- DOI:
- 10.1093/mnras/staa1434
- arXiv:
- arXiv:1812.05216
- Bibcode:
- 2020MNRAS.495.4237M
- Keywords:
-
- galaxies: evolution;
- galaxies: star formation;
- galaxies: statistics;
- radio continuum: galaxies;
- X-rays: galaxies;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- 11 pages, 6 figures. Accepted for publication in MNRAS