T-ReX: a graph-based filament detection method

Submitted to A&A, 16 pages, 16 figuresNumerical simulations and observations show that galaxies are not uniformly distributed in the universe but rather spread on 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 made of filaments. In the context of recent and upcoming large galaxy surveys, it becomes essential to identify and classify features of the Cosmic Web in an automatic way 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 to automatically retrieve the underlying filamentary structure from a 2D or 3D galaxy distribution using graph theory and the assumption that paths linking galaxies together with the minimum total length highlight the underlying distribution. To obtain a smoothed version of this topological prior, we embed it in a Gaussian mixtures framework. In addition to a geometrical description of the pattern, a bootstrap-like estimate of these regularized minimum spanning trees allows to obtain a map characterising the frequency at which an area of the domain is crossed. Using 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 few and comprehensible parameters