Fractal dimension of the cosmic web with different galaxy types

TL;DR

This study uses fractal dimensions to analyze the large-scale distribution of different galaxy types across cosmic time, revealing how galaxy populations trace the evolving cosmic web.

Contribution

It introduces a novel application of fractal dimension analysis to galaxy color types over a wide redshift range, enhancing understanding of large-scale structure mapping.

Findings

Blue galaxies have higher fractal dimensions than red and green at low redshift.

The fractal dimension gradient reverses at higher redshift, indicating evolving galaxy distribution patterns.

Fractal dimension effectively traces the cosmic web's evolution through galaxy color types.

Abstract

The fractal dimension $D$ is used to map the large-scale galaxy distribution in the Universe by color types: blue, green and red. Using a $NUVrK$-complete COSMOS2020 subsample of 618,952 galaxies observed up to $z=4$, number densities were derived and plotted against two cosmological distance measures, the luminosity and comoving (galaxy area) distances, in order to estimate $D$ for each galaxy color type in two redshift intervals: $z\gtrless1$. We found a general gradient $D_{\mathrm{blue}}> D_{\mathrm{red}}>D_{\mathrm{green}}$ with $D=1.40-2.03$ for $z<1$. For $1<z\leq4$, the gradient changes to $D_{\mathrm{blue}}>D_{\mathrm{green}}>D_{\mathrm{red}}$, and the fractal dimension values are lower, $D=0.03-0.44$. These results suggest that the fractal dimension is a sensitive diagnostic for how galaxy populations trace the evolving cosmic web, and confirm the fractal dimension as a useful tool for observational mapping of large-scale structure by galaxy color.