Environmental Effects on Galaxy Evolution

Abstract: Galaxies evolve within a web-like cosmic structure, and their properties are strongly shaped by their surrounding environments. We apply a nonparametric Bayesian two-sample test based on P\'olya tree priors to galaxy data from SDSS DR7 and DESI DR1 BGS to quantify the differences between galaxies in dense and sparse cosmic environments. Compared to the Kolmogorov-Smirnov test and parametric Bayesian test, our approach does not require strong assumptions about the underlying distributional form and provides a more sensitive and robust comparison of galaxy evolution across different environments. In particular, galaxies in VoidFinder voids tend to be fainter, less massive, and more star-forming compared to wall galaxies, while such contrasts are diminished under the V^2 REVOLVER pruning. These findings underscore the importance of both the statistical framework and the void classification algorithm in interpreting environmental effects on galaxy evolution.