Void Galaxies and Active Galactic Nucleus Activity in ZOBOV-identified TNG300 Voids from z = 3 to z = 0

Abstract We study void galaxies in the TNG300 simulation between redshifts z = 3 and z = 0. Cosmic void catalogs were constructed using a watershed-based void-finding algorithm, and we define four populations of field galaxies for our investigation: (1) galaxies that are members of a watershed void, (2) galaxies that are located within a radius r ≤ 0.8 R eff of the center of a void, (3) galaxies interior to spheres centered on void centers that have underdensity contrasts <–0.8, and (4) nonvoid galaxies. We show that population statistics on void galaxy properties can be recovered from watershed-based void catalogs. Differences between galaxy populations are most pronounced interior to the shell-crossing surface (i.e., population 3), where densities are intermediate to high. Compared to nonvoid galaxies at all redshifts, the density-controlled galaxies are bluer, smaller, more actively star-forming, more massive, and less metal-enriched. At redshifts ≥1, these differences are less apparent, likely caused by resolution and selection effects incurred by attempting to define a density-controlled sample from a watershed-based void-finding algorithm. Further, we investigate the fraction of galaxies with active galactic nuclei (AGN) and find that our density-controlled population has AGN fractions that are significantly higher than those of nonvoid galaxy populations (79.8% ± 0.4% higher at z = 0.0 and 61.5% ± 0.7% higher at larger redshifts).