Filaments from the galaxy distribution and from the velocity field in the local universe

TL;DR

This study compares two different algorithms for identifying cosmic filaments in the local universe, finding they agree well on complete data sets, thus supporting their effectiveness in tracing the Universe's large-scale structure.

Contribution

It demonstrates the consistency between the Bisous model and velocity shear web methods in mapping cosmic filaments using independent data sets.

Findings

Good agreement between methods in the local universe within 100 Mpc.

Better agreement when applied to simulation data than observational data.

Both methods likely accurately trace the underlying matter distribution.

Abstract

The cosmic web that characterizes the large-scale structure of the Universe can be quantified by a variety of methods. For example, large redshift surveys can be used in combination with point process algorithms to extract long curvilinear filaments in the galaxy distribution. Alternatively, given a full 3D reconstruction of the velocity field, kinematic techniques can be used to decompose the web into voids, sheets, filaments and knots. In this paper we look at how two such algorithms - the Bisous model and the velocity shear web - compare with each other in the local Universe (within 100 Mpc), finding good agreement. This is both remarkable and comforting, given that the two methods are radically different in ideology and applied to completely independent and different data sets. Unsurprisingly, the methods are in better agreement when applied to unbiased and complete data sets, like cosmological simulations, than when applied to observational samples. We conclude that more observational data is needed to improve on these methods, but that both methods are most likely properly tracing the underlying distribution of matter in the Universe.