A continuous parameterization of the cosmic web

TL;DR

This paper introduces a continuous framework for classifying cosmic environments using Hessian eigenvalues, providing a nuanced understanding of how galaxy properties depend on their surroundings beyond traditional fixed categories.

Contribution

It proposes a novel continuous environmental classification method based on Hessian eigenvalues, enhancing the analysis of galaxy-environment relationships in simulations and models.

Findings

Eigenvalue ratios show a continuous distribution correlating with galaxy properties.

Critical values mark transitions in galaxy behavior related to environment.

The method improves understanding of galaxy formation influenced by environment.

Abstract

The intrinsic properties of galaxies are influenced by their environments, underscoring the environment's critical role in galaxy formation and evolution. Traditionally, these environments are categorized into four fixed classifications: knots, filaments, walls, and voids, which collectively describe the complex organization of galaxies within large-scale structures. We propose an alternative description that complements the traditional quadripartite categorization by introducing a continuous framework, allowing for a more nuanced examination of the relationship between the intrinsic properties of galaxies and their environments. This complementary description is applied using one of the most prevalent methodologies: categorization using the eigenvalues of the Hessian matrix extracted from the matter density field. We integrated our findings into a semi-analytical model of galaxy formation, combined with cosmological numerical simulations, to analyze how the intrinsic properties of galaxies are influenced by environmental changes. In our study, we find a continuous distribution of eigenvalue ratios, revealing a clear dependence of galaxy properties on their surrounding environments. This method allowed us to identify critical values at which transitions in the behavior of key astrophysical galaxy properties become evident.