Distinct origins of environmentally quenched galaxies in the core and outer virialised regions of massive clusters at $0.8<z<1.5$

TL;DR

This study investigates how galaxy quenching processes differ between cluster cores and outskirts at high redshift, revealing distinct mechanisms like early mass-quenching in cores and environmental quenching in outer regions.

Contribution

It introduces a Bayesian model to analyze the radial and redshift dependence of galaxy quenching, highlighting different dominant mechanisms in cluster cores versus outskirts at $0.8<z<1.5$.

Findings

Quenched fraction is higher in cluster cores (~70%) than outskirts (~40%).

Quiescent SMF in outskirts resembles field, while core resembles quiescent field.

Different quenching mechanisms dominate in core (early mass-quenching) and outskirts (environmental-quenching).

Abstract

High-redshift ($z\sim1$) galaxy clusters are the domain where environmental quenching mechanisms are expected to emerge as important factors in the evolution of the quiescent galaxy population. Uncovering these initially subtle effects requires exploring multiple dependencies of quenching across the cluster environment, and through time. We analyse the stellar-mass functions (SMFs) of 17 galaxy clusters within the GOGREEN and GCLASS surveys between $0.8<z<1.5$, and with $\log{(M/{\rm{M_\odot}})}>9.5$. The data are fit simultaneously with a Bayesian model that allows the Schechter function parameters of the quiescent and star-forming populations to vary smoothly with cluster-centric radius and redshift. The model also fits the radial galaxy number density profile of each population, allowing the global quenched fraction to be parameterised as a function of redshift and cluster velocity dispersion. We find the star-forming SMF to not depend on radius or redshift. For the quiescent population however, there is $\sim2\sigma$ evidence for a radial dependence. Outside the cluster core ($R>0.3\,R_{\rm200}$), the quenched fraction above $\log{(M/{\rm{M_\odot}})}=9.5$ is $\sim40{\rm\;per\,cent}$, and the quiescent SMF is similar in shape to the star-forming field. In contrast, the cluster core has an elevated quenched fraction ($\sim70{\rm\;per\,cent}$), and a quiescent SMF similar in shape to the quiescent field population. We explore contributions of 'early mass-quenching' and mass-independent 'environmental-quenching' models in each of these radial regimes. The core is well-described primarily by early mass-quenching, which we interpret as accelerated quenching of massive galaxies in protoclusters, possibly through merger-driven feedback mechanisms. The non-core is better described through mass-independent, environmental-quenching of the infalling field population.