The mass-size relation of galaxy clusters

TL;DR

This paper investigates the physical boundary of galaxy clusters using simulations, revealing a connection between the cluster edge, filament orientation, and galaxy profiles, and proposes a new mass-size relation for cosmology.

Contribution

It establishes a link between the splashback feature in dark matter and galaxy profiles, proposing a novel observational mass-size relation for galaxy clusters.

Findings

The splashback feature correlates with filament direction.

Galaxy profiles can define a cluster mass-size relation.

This relation can be used for cosmological studies.

Abstract

The outskirts of accreting dark matter haloes exhibit a sudden drop in density delimiting their multi-stream region. Due to the dynamics of accretion, the location of this physically motivated edge strongly correlates with the halo growth rate. Using hydrodynamical zoom-in simulations of high-mass clusters, we explore this definition in realistic simulations and find an explicit connection between this feature in the dark matter and galaxy profiles. We also show that the depth of the splashback feature correlates well with the direction of filaments and, surprisingly, the orientation of the brightest cluster galaxy. Our findings suggest that galaxy profiles and weak-lensing masses can define an observationally viable mass-size scaling relation for galaxy clusters, which can be used to extract cosmological information.