At Least One-in-Six Galaxies Is Always Dead

TL;DR

This paper demonstrates through numerical experiments that a significant fraction of galaxies are passive at high redshift due to stochastic star formation histories, suggesting a universal baseline of galaxy quiescence.

Contribution

It introduces a model linking passive galaxy fractions to maximally correlated stochastic star formation histories, explaining observations across different epochs and masses.

Findings

Passive fraction at high redshift is consistent with stochastic processes.

Baseline passive fraction remains constant across epochs and mass regimes.

Future JWST data should confirm these predictions.

Abstract

Via numerical experiments, we show that the $\sim$10%-20% passive fraction seen at $z>3$ is consistent with galaxy star formation histories being maximally correlated stochastic processes. If so, this fraction should reflect a time-independent baseline that holds at any epoch or mass regime where mean star formation rates are rising. Data at $\log M_\ast<10$ and $z<0.5$ bear this out, as should future James Webb Space Telescope observations.