Observing dynamical friction in galaxy clusters

TL;DR

This paper introduces a new observational method to detect dynamical friction effects in galaxy clusters by analyzing the spatial distribution of satellite galaxies, confirming the effect with SDSS data.

Contribution

The study develops a novel stacking technique and toy model to observe dynamical friction effects in real galaxy clusters, validated with SDSS data.

Findings

Bright satellites have smaller splashback radii than fainter ones.

The effect of dynamical friction is detected at 99% confidence.

The toy model reproduces trends observed in simulations.

Abstract

We present a novel method to detect the effects of dynamical friction in observed galaxy clusters. Following accretion into clusters, massive satellite galaxies will backsplash to systematically smaller radii than less massive satellites, an effect that may be detected by stacking the number density profiles of galaxies around clusters. We show that this effect may be understood using a simple toy model which reproduces the trends with halo properties observed in simulations. We search for this effect using SDSS redMaPPer clusters with richness 10<lambda<20, and find that bright (M_i<-21.5) satellites have smaller splashback radii than fainter (M_i>-20) satellites at 99% confidence.