The formation of massive, quiescent galaxies at cosmic noon

TL;DR

This study uses high-resolution cosmological simulations to show that the specific accretion rate of dark matter halos is a key factor in determining when massive galaxies at cosmic noon become quiescent, independent of black hole feedback.

Contribution

It identifies halo accretion rate as a primary determinant of galaxy quiescence at cosmic noon, challenging the emphasis on black hole feedback effects.

Findings

Halos with low specific accretion rates host quiescent galaxies.

The fraction of such halos matches observed quiescent galaxy fractions.

Halo accretion rate should be included in galaxy evolution models.

Abstract

The cosmic noon (z~1.5-3) marked a period of vigorous star formation for most galaxies. However, about a third of the more massive galaxies at those times were quiescent in the sense that their observed stellar populations are inconsistent with rapid star formation. The reduced star formation activity is often attributed to gaseous outflows driven by feedback from supermassive black holes, but the impact of black hole feedback on galaxies in the young Universe is not yet definitively established. We analyze the origin of quiescent galaxies with the help of ultra-high resolution, cosmological simulations that include feedback from stars but do not model the uncertain consequences of black hole feedback. We show that dark matter halos with specific accretion rates below ~0.25-0.4 per Gyr preferentially host galaxies with reduced star formation rates and red broad-band colors. The fraction of such halos in large dark matter only simulations matches the observed fraction of massive quiescent galaxies (~10^10-10^11 Msun). This strongly suggests that halo accretion rate is the key parameter determining which massive galaxies at z~1.5-3 become quiescent. Empirical models that connect galaxy and halo evolution, such as halo occupation distribution or abundance matching models, assume a tight link between galaxy properties and the masses of their parent halos. These models will benefit from adding the specific accretion rate of halos as a second model parameter.