Properties of Voids and Void Galaxies in the TNG300 Simulation

Abstract

We investigate the properties of voids and void galaxies in the TNG300 simulation. Using a luminous galaxy catalog and a spherical void-finding algorithm, we identify 5078 voids at redshift z = 0. The voids cover 83% of the simulation volume and have a median radius of 4.4 h −1 Mpc. We identify two populations of field galaxies based on whether the galaxies reside within a void (“void galaxies”; 75,220 objects) or outside a void (“nonvoid galaxies”; 527,454 objects). Within the voids, mass does not directly trace light. Instead, the mean radial underdensity profile as defined by the locations of void galaxies is systematically lower than the mean radial underdensity profile as defined by the dark matter (i.e., the voids are more “devoid” of galaxies than they are of mass). Within the voids, the integrated underdensity profiles of the dark matter and the galaxies are independent of the local background density (i.e., voids-in-voids versus voids-in-clouds). Beyond the void radii, however, the integrated underdensity profiles of both the dark matter and the galaxies exhibit strong dependencies on the local background density. Compared to nonvoid galaxies, void galaxies are on average younger, less massive, bluer in color, less metal enriched, and have smaller radii. In addition, the specific star formation rates of void galaxies are ∼20% higher than nonvoid galaxies and, in the case of galaxies with central supermassive black holes with M BH ≳ 3 × 106 h −1 M ⊙, the fraction of active void galaxies is ∼25% higher than active nonvoid galaxies.