Continuous Filament Network of the Local Universe

Abstract

Simulated galaxy distributions are suitable for developing filament detection algorithms. However, samples of observed galaxies, being of limited size, cause difficulties that lead to a discontinuous distribution of filaments. We created a new galaxy filament catalog composed of a continuous cosmic web with no lone filaments. The core of our approach is a ridge filter used within the framework of image analysis. We considered galaxies from the HyperLeda database with redshifts $0.02\leqslant z\leqslant 0.1$, and in the solid angle $120^\circ\leqslant {\rm RA}\leqslant 240^\circ$, $0^\circ\leqslant {\rm DEC}\leqslant 60^\circ$. We divided the sample into 16 two-dimensional celestial projections with redshift bin $\Delta z=0.005$, and compared our continuous filament network with a similar recent catalog covering the same region of the sky. We tested our catalog on two application scenarios. First, we compared the distributions of distance to nearest filament of various astrophysical sources (Seyfert galaxies and other active galactic nuclei, radio galaxies, low surface brightness galaxies, and dwarf galaxies), and found that all source types trace the filaments well, with no systematic differences. Next, among the HyperLeda galaxies, we investigated the dependence of $g-r$ color distribution on distance to nearest filament, and confirmed that early type galaxies are located on average further from the filaments than late type ones.