Radial dependence of galaxy and halo properties in cosmic voids: SDSS DR7 and the ELUCID constrained simulation

Abstract

Cosmic voids provide a setting for examining the interplay between mass and environment in shaping galaxy and halo properties. Using the SDSS DR7 volume-limited galaxy sample and the ELUCID constrained simulation of the local large-scale structure, we investigate the radial profiles of galaxy and subhalo properties across different mass ranges, identifying voids independently in the observed galaxy and simulated subhalo distributions. Both stellar mass and subhalo mass increase from void interiors toward the void boundary, indicating that lower-mass galaxies and subhaloes preferentially reside in void interiors. The satellite fraction of subhaloes also increases systematically toward the void boundary. Galaxy colour and specific star formation rate exhibit radial variations that are weaker than their dependence on stellar mass, while the spiral fraction shows little radial dependence at fixed stellar mass. For dark-matter haloes, the apparent radial increase in size within a broad high-mass bin largely disappears when narrower mass ranges are considered. Halo concentration and spin show radial variations at fixed mass, with higher concentrations and lower spins toward void interiors, although the concentration trend is less pronounced in the extended low-mass sample. The formation redshift of low-mass subhaloes also increases toward the void boundary, whereas this dependence weakens and eventually disappears at higher masses. Overall, the radial trends in galaxy properties are generally weaker than their mass dependence, while several subhalo properties retain measurable radial variations at fixed mass.