Anisotropic quenching beyond $z=1$ and its implications for preprocessing around high-redshift galaxy clusters

Abstract

Recent studies have shown that, within galaxy clusters, quenched satellite galaxies tend to be distributed preferentially along the major axis of the central galaxy, dubbed anisotropic quenching. There are various discussions about the origin of this anisotropy: some link it to active galactic nucleus activity in the central galaxy, while others attribute it to the preprocessing of galaxies within large-scale structures outside clusters. However, the definitive cause and its redshift dependence remain unclear. In this study, we investigate anisotropic quenching with 12 spectroscopically confirmed galaxy clusters at $0.9<z<1.4$. We calculate the quiescent satellite galaxy fraction as a function of orientation angle measured from the central galaxy's major axis. Although the statistical significance is modest ($\sim 2σ$), we detect anisotropic quenching in the highest redshift ever. To understand the origin of the observed anisotropy, we examine the accretion history of satellite galaxies in a cosmological simulation. We find that, in the $z=1.25$ clusters, the majority of satellite galaxies are recently ($\lesssim 2\,\mathrm{Gyr}$) infalled galaxies. In addition, the orientation angles of satellites are randomized immediately after accretion in $\sim 2\,\mathrm{Gyr}$, suggesting that only recently accreted galaxies contribute to the observed anisotropy. We adopt a semi-analytic approach that combines the accretion history of satellite galaxies with a quenching model based on a delay-then-rapid quenching framework and parameterizes both intrahalo quenching and preprocessing effects. We find that preprocessing is the dominant contributor to quenching and that the quenched fraction attributable to preprocessing is higher along the major axis than along the minor axis by $\sim20\%$, reproducing the observed anisotropic quenching signal.