Properties of Voids and Void Galaxies in the TNG300 Simulation

We investigate the properties of voids and void galaxies in the \texttt{TNG300} simulation. Using a luminous galaxy catalog and a spherical void finding algorithm, we identify 5,078 voids at redshift $z = 0$. 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 vs.\ 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 non-void 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 $\sim 20$\% higher than non-void galaxies and, in the case of galaxies with central supermassive black holes with $M_{\rm BH} \gtrsim 3\times 10^6 h^{-1} M_\odot$, the fraction of active void galaxies is $\sim 25$\% higher than active non-void galaxies.