Massive and old quiescent galaxies at high redshift

TL;DR

This paper develops color-color diagrams to identify massive quiescent galaxies at high redshift, revealing their abundance exceeds current model predictions and highlighting the need for improved quenching mechanisms in galaxy evolution models.

Contribution

It introduces a new method using observer-frame color-color diagrams for selecting high-redshift quiescent galaxies, and compares their observed abundance to theoretical models.

Findings

Number of massive old quiescent galaxies exceeds model predictions

Refined selection with SED fitting improves candidate identification

Highlights need for improved high-redshift quenching mechanisms

Abstract

Massive quiescent galaxies at high redshift can shed light on the processes of galaxy mass assembly and quenching of the star formation at early epochs. We present observer-frame color-color diagrams designed to identify candidate quiescent galaxies from z=2.5 up to the highest redshifts, that can be then be selected for spectroscopic follow-up observations. The application to the COSMOS2015 catalog shows that, after refining the selection with SED fitting, the number of massive old quiescent galaxies exceeds the forecast of state-of-the-art semi-analytic models, pointing out the need of an improvement of the implemented quenching mechanisms at high redshifts.