arXiv subjects

Benjamin Hertzsch

Publications and source records attributed to Benjamin Hertzsch.

3 recordsLinked to original sources

arXiv2026

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

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]

astro-ph.CO↗

arXiv2026

Galaxy Populations in the IllustrisTNG Caustic Skeleton

The caustic skeleton is a parameter-free and mathematically rigorous formalism for tracing the hierarchical formation history of the multiscale cosmic web from the singularities in the underlying dark matter flow. In the present study, we explicitly use the multistreaming nature of the cosmic mass distribution to address the influence of the weblike embedding on the galaxy populations and discern their properties in different web environments. To this end, we construct the multiscale caustic skeleton of the dark mass distribution in the state-of-the-art suite of the large-scale IllustrisTNG simulations. In addition to the multistreaming dark matter density field, we assess the characteristic properties of the intergalactic baryonic gas in the vicinity of the caustics. Next, we associate the galaxies with the voids, walls, filaments and cluster nodes, and investigate their colours and star formation activities. A unique feature of the analysis is that it explicitly addresses the multiscale aspects with respect to the galaxy population, assessing issues such as the fraction of (blue) galaxies as a function of the scale of the cosmic web pattern and its caustic features. We find that the galaxy properties form a continuum in the scale-space cosmic web. Intimately coupled to the hierarchical build-up of the cosmic structure, it also allows us to systematically assess the impact of the formation time of the various structural components of the cosmic web on the galaxy properties. This furthers insight into the establishment of the observed colour-density relation of galaxies.

astro-ph.CO↗

arXiv2025

A New Recipe for Caustic Pancakes: On the Reality of Walls in the Cosmic Web

The caustic skeleton model is a mathematically rigorous framework for studying the formation history of the emerging cosmic web from the caustics in the underlying dark matter flow. In a series of two papers, we use constrained N-body simulations to investigate the different cosmic web environments. For the current study, we focus on the cosmic walls. We derive the conditions of the centres of proto-walls and analyse their evolution with N-body simulations. Next, we investigate the statistical properties of Zel'dovich pancakes by studying the number density of the cosmic wall centres in scale space and, for the first time, we calculate the Lagrangian-space volume of cosmic walls. Finally, we infer the mean density and velocity fields and the distribution of haloes around cosmic walls with a suite of physically realistic dark-matter-only simulations. We compare the cosmic walls obtained with the caustic skeleton framework with previously proposed saddle point conditions on the primordial potential and density perturbation.

astro-ph.CO↗