Local-Group tests of dark-matter Concordance Cosmology: Towards a new paradigm for structure formation

TL;DR

This paper compares the predictions of the standard cosmological model with Local Group galaxy observations, uncovers significant discrepancies, and suggests alternative formation scenarios involving tidal dwarf galaxies to resolve these issues.

Contribution

It identifies five major problems with the standard model's predictions for Local Group structures and proposes that tidal dwarf galaxy formation processes may offer a viable alternative explanation.

Findings

Five irreconcilable problems with the standard model predictions.

Evidence linking bulge formation and satellite properties to tidal interactions.

Potential of tidal dwarf galaxies as an alternative explanation for satellite populations.

Abstract

(abridged) Predictions of the Concordance Cosmological Model (CCM) of the structures in the environment of large spiral galaxies are compared with observed properties of Local Group galaxies. Five new most probably irreconcilable problems are uncovered. However, the Local Group properties provide hints that may lead to a solution of the above problems The DoS and bulge--satellite correlation suggest that dissipational events forming bulges are related to the processes forming phase-space correlated satellite populations. Such events are well known to occur since in galaxy encounters energy and angular momentum are expelled in the form of tidal tails, which can fragment to form populations of tidal-dwarf galaxies (TDGs) and associated star clusters. If Local Group satellite galaxies are to be interpreted as TDGs then the sub-structure predictions of CCM are internally in conflict. All findings thus suggest that the CCM does not account for the Local Group observations and that therefore existing as well as new viable alternatives have to be further explored. These are discussed and natural solutions for the above problems emerge.