Caustic Skeleton and the Local Cosmic Web: the Coma Cluster node and the Pisces-Perseus ridge

TL;DR

This paper applies caustic skeleton theory to reconstruct and classify large-scale cosmic web structures like the Coma Cluster and Pisces-Perseus ridge, revealing new topological distinctions and hierarchical organization.

Contribution

It introduces a multi-scale caustic skeleton approach to analyze the cosmic web, identifying topologically distinct filament classes and their influence on local galaxy environments.

Findings

Caustic skeleton network accurately reproduces galaxy organization in simulations.

Identifies two topologically distinct filament classes with different formation histories.

Reveals the Pisces-Perseus Supercluster as D_4-dominated, highlighting topological diversity.

Abstract

We apply caustic skeleton theory to the Manticore-Local simulations, which are Bayesian constrained reconstructions of the Local Universe from the 2M++ galaxy catalogue, and extract the three-dimensional multi-scale caustic skeleton of two canonical weblike structures in our Local Universe, namely the Coma Cluster and the Pisces-Perseus ridge as they represent the most prominent cluster node and filamentary artery in the nearby Universe. We show that the Caustic Skeleton network of caustic singularities accurately reproduces the observed large-scale organisation of galaxies in redshift space for one of the Manticore realisations. The hierarchy of caustic features allows us to establish a multi-scale classification of the large-scale environment in which observed 2M++ galaxies reside. One of the most interesting aspects of the theory is that it predicts two topologically distinct classes of filaments (A_4 swallowtail and D_4 umbilic caustics) that form through fundamentally different folding histories yet appear morphologically similar enough, on the surface, to be overlooked by conventional structure identifiers. We find that the influence of D_4 filaments only becomes increasingly relevant towards smaller scales, and the Pisces-Perseus Supercluster in particular is revealed to be a distinctly D_4-dominated structure compared to the extended Stickman structure around the Coma Cluster. In other words, caustic skeleton theory enables a novel topological characterisation of one of the most studied filamentary complexes in the nearby Universe. [Shortened]