The alignment of satellite galaxies and cosmic filaments: observations and simulations

TL;DR

This study confirms that satellite galaxies tend to align with cosmic filaments, supporting theories that structure formation influences galaxy accretion patterns, with stronger alignments observed in redder, brighter galaxies.

Contribution

It provides observational evidence for satellite-filament alignment and compares these findings with simulations, highlighting the influence of the cosmic web on galaxy accretion.

Findings

Significant satellite-filament alignment observed in SDSS data.

Alignment strength depends on galaxy color and brightness.

Simulations qualitatively agree with observational results.

Abstract

The accretion of satellites onto central galaxies along vast cosmic filaments is an apparent outcome of the anisotropic collapse of structure in our Universe. Numerical work (based on gravitational dynamics of N-body simulations) indicates that satellites are beamed towards hosts along preferred directions imprinted by the velocity shear field. Here we use the Sloan Digital Sky Survey to observationally test this claim. We construct 3D filaments and sheets and examine the relative position of satellite galaxies. A statistically significant alignment between satellite galaxy position and filament axis in observations is confirmed. We find a qualitatively compatible alignments by examining satellites and filaments similarly identified in the Millennium simulation, semi-analytical galaxy catalogue. We also examine the dependence of the alignment strength on galaxy properties such as colour, magnitude and (relative) satellite magnitude, finding that the alignment is strongest for the reddest and brightest central and satellite galaxies. Our results confirm the theoretical picture and the role of the cosmic web in satellite accretion. Furthermore our results suggest that filaments identified on larger scales can be reflected in the positions of satellite galaxies that are quite close to their hosts.