T-ReX: a graph-based filament detection method

TL;DR

This paper introduces T-ReX, a novel graph-based method for automatically detecting filamentary structures in galaxy distributions, leveraging minimum spanning trees and Gaussian mixture models to robustly identify cosmic web features.

Contribution

The paper presents a new approach combining graph theory and Gaussian mixtures to accurately and automatically extract filamentary structures from galaxy data, including noise and outliers robustness.

Findings

Successfully recovers filamentary patterns in simulated galaxy distributions.

Robust to noise and outliers with minimal parameters.

Effective in 2D and 3D galaxy datasets.

Abstract

Numerical simulations and observations show that galaxies are not uniformly distributed in the universe but, rather, they are spread across a filamentary structure. In this large-scale pattern, highly dense regions are linked together by bridges and walls, all of them surrounded by vast, nearly-empty areas. While nodes of the network are widely studied in the literature, simulations indicate that half of the mass budget comes from a more diffuse part of the network, which is made up of filaments. In the context of recent and upcoming large galaxy surveys, it becomes essential that we identify and classify features of the Cosmic Web in an automatic way in order to study their physical properties and the impact of the cosmic environment on galaxies and their evolution. In this work, we propose a new approach for the automatic retrieval of the underlying filamentary structure from a 2D or 3D galaxy distribution using graph theory and the assumption that paths that link galaxies together with the minimum total length highlight the underlying distribution. To obtain a smoothed version of this topological prior, we embedded it in a Gaussian mixtures framework. In addition to a geometrical description of the pattern, a bootstrap-like estimate of these regularised minimum spanning trees allowed us to obtain a map characterising the frequency at which an area of the domain is crossed. Using the distribution of halos derived from numerical simulations, we show that the proposed method is able to recover the filamentary pattern in a 2D or 3D distribution of points with noise and outliers robustness with a few comprehensible parameters.