Studying Inter-Cluster Galaxy Filaments Through Stacking GMBCG Galaxy Cluster Pairs

TL;DR

This paper introduces a stacking method using SDSS data to detect and analyze the properties of inter-cluster galaxy filaments, revealing their color, luminosity, and redshift evolution, with implications for future surveys.

Contribution

The study presents a novel stacking technique to detect filament overdensities and analyze their galaxy populations using photometric data, extending understanding of filament properties.

Findings

Filament galaxies are bimodal in color and contain more blue galaxies than clusters.

Filament galaxies are generally fainter than cluster galaxies.

The blue galaxy fraction in filaments increases with redshift, indicating a redshift evolution.

Abstract

We present a method to study the photometric properties of galaxies in filaments by stacking the galaxy populations between pairs of galaxy clusters. Using Sloan Digital Sky Survey data, this method can detect the inter-cluster filament galaxy overdensity with a significance of $\sim 5 \sigma$ out to $z=0.40$. Using this approach, we study the $g-r$ color and luminosity distribution of filament galaxies as a function of redshift. Consistent with expectation, filament galaxies are bimodal in their color distribution and contain a larger blue galaxy population than clusters. Filament galaxies are also generally fainter than cluster galaxies. More interestingly, the observed filament population seems to show redshift evolution at $0.12<z<0.40$: the blue galaxy fraction has a trend to increase at higher redshift: a filament "Butcher Oemler Effect". We test the dependence of the observed filament density on the richness of the cluster pair: richer clusters are connected by higher density filaments. We also test the spatial dependence of filament galaxy overdensity: this quantity decreases when moving away from the inter-cluster axis between a cluster pair. This method provides an economical way to probe the photometric properties of filament galaxies and should prove useful for upcoming projects like the Dark Energy Survey.