The first quenched galaxies, when and how?

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 $685\mathrm{Mpc}$ on a side, the first quenched massive ($M_{\star }\sim 10^{11}{\mathrm{M}}_{\odot }$), Milky Way mass, and low mass ($M_{\star }\sim 10^{9.5}{\mathrm{M}}_{\odot }$ ) 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.

8 pages, 3 figures, Accepted publication in APJL