Void Galaxy Distribution: A Challenge for $\Lambda$CDM

TL;DR

This study compares void galaxy distributions from SDSS observations and Millennium simulations, revealing discrepancies in galaxy separation, void center proximity, and density profiles that challenge the $\

Contribution

It provides a detailed comparison of void galaxy properties between observations and simulations, highlighting significant differences that test $\

Findings

Observed void galaxies are closer to void centers than in simulations.

Void galaxies in observations have larger mean distances than in simulations.

Central densities of observed voids are higher than those predicted by simulations.

Abstract

We extract void catalogs from the Sloan Digital Sky Survey Data Release 16 (SDSS DR16) survey and also from the Millennium simulation. We focus our comparison on distribution of galaxies brighter than $M_r < -18$ inside voids and study the mean separation of void galaxies, distance from the void center, and the radial density profile. We find that mean separation of void galaxies depends on void size, as bigger voids have lower mean separation in both samples. However, void galaxies in the observation sample seem to have generally larger mean-distance than simulated ones at any given void size. In addition, observed void galaxies tend to reside closer to the void center than those in the simulation. This discrepancy is also shown in the density profile of voids. Regardless of the void size, the central densities of real void profiles are higher than the ones in the predicted simulated catalog.