On the sociology and hierarchy of voids: a study of seven CAVITY nearby galaxy voids and their dynamical CosmicFlows-3 environment

On the sociology and hierarchy of voids: a study of seven CAVITY nearby galaxy voids and their dynamical CosmicFlows-3 environment by H. M. Courtois et al. on Wednesday 30 November Context. The present study addresses a key question for our understanding of the relation between void galaxies and their environment: the relationship between luminous and dark matter in and around voids. Aims. To explore how empty of matter local Universe voids are, we study the full (dark+luminous) matter content of seven nearby cosmic voids that are fully contained within the CosmicFlows-3 volume. Methods. The cosmic voids matter density profiles are independently obtained using two different methods. They are built on one hand from the galaxy redshift space 2 points-correlation function and, on the other hand, using peculiar velocity gradients from the CosmicFlows-3 dataset. Results. The results are noticeable since when using the redshift survey, all voids show a radial positive gradient of galaxies, while based on the dynamical analysis, only three of these voids display a clear underdensity of matter in their center. Conclusions. It is the first time such a detailed observational analysis of voids is conducted, showing that void emptiness should be derived from dynamical information. Yet, from this limited study, the Hercules void is the best candidate for a local Universe pure "pristine volume" expanding in 3 directions with no dark matter located in that void. arXiv: http://arxiv.org/abs/http://arxiv.org/abs/2211.16388v1