Missing Dark Matter in the Local Universe

TL;DR

This study reveals a significant discrepancy between local and global matter densities, suggesting that most dark matter may not be associated with galaxy clusters or groups, challenging current cosmological models.

Contribution

It introduces a new perspective on dark matter distribution, proposing that most dark matter is outside galaxy clusters and groups, which explains the local underdensity.

Findings

Local matter density Omega_m,loc=0.08+-0.02

Global matter density Omega_m,glob=0.28+-0.03

Dark matter may be distributed outside clusters

Abstract

A sample of 11 thousand galaxies with radial velocities V_ LG < 3500 km/s is used to study the features of the local distribution of luminous (stellar) and dark matter within a sphere of radius of around 50 Mpc around us. The average density of matter in this volume, Omega_m,loc=0.08+-0.02, turns out to be much lower than the global cosmic density Omega_m,glob=0.28+-0.03. We discuss three possible explanations of this paradox: 1) galaxy groups and clusters are surrounded by extended dark halos, the major part of the mass of which is located outside their virial radii; 2) the considered local volume of the Universe is not representative, being situated inside a giant void; and 3) the bulk of matter in the Universe is not related to clusters and groups, but is rather distributed between them in the form of massive dark clumps. Some arguments in favor of the latter assumption are presented. Besides the two well-known inconsistencies of modern cosmological models with the observational data: the problem of missing satellites of normal galaxies and the problem of missing baryons, there arises another one - the issue of missing dark matter.