The first quenched galaxies, when and how?

TL;DR

This study uses the GAEA semi-analytic model to predict the emergence and mechanisms of quenching in galaxies from redshift 7 to 4.5, highlighting early black hole feedback as the main driver.

Contribution

It provides the first predictions for quenching fractions up to redshift 7 and identifies the dominant quenching mechanisms at different epochs.

Findings

First quenched galaxies appear at z~4.5, 6.2, and before z=7.

Most early quenched galaxies remain quenched for over 1 Gyr.

Black hole feedback via mergers and disk instabilities drives early quenching.

Abstract

Many quiescent galaxies discovered in the early Universe by \textit{JWST} raise fundamental questions on when and how these galaxies became and stayed quenched. Making use of the latest version of the semi-analytic model GAEA that provides good agreement with the observed quenched fractions up to $z\sim 3$, we make predictions for the expected fractions of quiescent galaxies up to $z\sim 7$ and analyze the main quenching mechanism. We find that in a simulated box of $685~{\rm Mpc}$ on a side, the first quenched massive ($M_{\star} \sim 10^{11} {\rm M}_{\odot}$), Milky Way mass, and low mass ($M_{\star} \sim 10^{9.5} {\rm M}_{\odot}$ ) galaxies appear at $z\sim 4.5$, $z\sim 6.2$, and before $z = 7$. Most quenched galaxies identified at early redshifts remain quenched for more than 1 Gyr. Independently of galaxy stellar mass, the dominant quenching mechanism at high redshift is accretion disk feedback (quasar winds) from a central massive black hole, which is triggered by mergers in massive and MW-mass galaxies, and by disk instabilities in low-mass galaxies. Environmental stripping becomes increasingly more important at lower redshift.