Anisotropic infall in the outskirst of clusters

TL;DR

This study investigates how galaxy infall modes in cluster outskirts influence star formation quenching, revealing that filamentary infall leads to stronger quenching than isotropic infall, especially at larger radii and lower redshifts.

Contribution

It provides a detailed analysis of the environmental effects on galaxy evolution in cluster outskirts using semi-analytic models and simulation data, highlighting the role of filamentary infall.

Findings

Star formation levels are intermediate in infall regions.

Stronger quenching occurs in filamentary infall regions.

Red galaxy fraction increases with radius, especially in filaments.

Abstract

We analyse the connection between the star formation quenching of galaxies and their location in theoutskirts of clusters in the redshift range $z=[0,2]$ by estimating the fraction of red galaxies. More specifically, we focus on galaxies that infall isotropically from those that are infalling alongside filaments. We use a sample of galaxies obtained from the semi-analytic model of galaxy formation SAG applied to the MultiDark simulation. {\textsc{mdpl2}}. In agreement with observational results, we find that the infall regions show levels of star formation that are intermediate between those of galaxies in clusters and in the field. Moreover, we show that, in the redshift range [0-0.85], the quenching of the star formation is stronger in the filamentary region than in the isotropic infall region. We also study the fraction of red galaxies as a function of the normalised distance to the cluster centre and find that, for radii $R/R_{200}> 3 $, the fraction of red galaxies in the filamentary region is considerably larger than in the isotropic infall region. From the analysis of properties of the main progenitors of galaxies identified at $z = 0$, we find that they have different evolutionary behaviours depending on the stellar mass and environment. Our results confirm the observational findings that suggest that the infall regions of clusters play an important role in the pre-processing of galaxies along most of the evolutionary history of galaxies.