Detection of anisotropic satellite quenching in galaxy clusters up to $z\sim1$

TL;DR

This study detects anisotropic satellite galaxy quenching relative to central galaxy axes up to redshift 1, revealing that quenching efficiency varies with orientation and is likely driven by rapid environmental processes like ram-pressure stripping.

Contribution

First detection of orientation-dependent satellite quenching up to z~1 using a large optical cluster sample, highlighting the role of physical processes with short quenching timescales.

Findings

Quenching anisotropy is significant in cluster cores but not outskirts.

Quenching efficiency is nearly independent of stellar mass.

Anisotropic quenching suggests rapid environmental mechanisms like ram-pressure stripping.

Abstract

Satellite galaxies in the cluster environment are more likely to be quenched than galaxies in the general field. Recently, it has been reported that satellite galaxy quenching depends on the orientation relative to their central galaxies: satellites along the major axis of centrals are more likely to be quenched than those along the minor axis. In this paper, we report a detection of such anisotropic quenching up to $z\sim1$ based on a large optically-selected cluster catalogue constructed from the Hyper Suprime-Cam Subaru Strategic Program. We calculate the quiescent satellite galaxy fraction as a function of orientation angle measured from the major axis of central galaxies and find that the quiescent fractions at $0.25<z<1$ are reasonably fitted by sinusoidal functions with amplitudes of a few percent. Anisotropy is clearer in inner regions ($<r_\mathrm{200m}$) of clusters and not significant in cluster outskirts ($>r_\mathrm{200m}$). We also confirm that the observed anisotropy cannot be explained by differences in local galaxy density or stellar mass distribution along the two axes. Quiescent fraction excesses between the two axes suggest that the quenching efficiency contributing to the anisotropy is almost independent of stellar mass, at least down to our stellar mass limit of $M_{*}=1\times10^{10}\,M_{\odot}$. Finally, we argue that the physical origins of the observed anisotropy should have shorter quenching timescales than $\sim1\,\mathrm{Gyr}$, like ram-pressure stripping, because, for anisotropic quenching to be observed, satellites must be quenched before their initial orientation angles are significantly changed.