Galaxy Group Ellipticity Confirms a Younger Cosmos

TL;DR

This study compares galaxy group ellipticities in observations and simulations, finding observed groups are more elongated, supporting the idea of a younger universe than predicted by standard cosmological models.

Contribution

It provides evidence of a discrepancy in galaxy group shapes between observations and Lambda CDM simulations, implying a potentially younger universe.

Findings

Observed galaxy groups are more elliptical than simulated ones.

The ellipticity discrepancy is statistically significant at about 4 sigma.

Results support the hypothesis of a younger universe than current models suggest.

Abstract

We present an analysis of the ellipticities of galaxy groups, derived from the spatial distribution of member galaxies, revealing a notable incongruity between the observed local galaxy groups and their counterparts in the Lambda cold dark matter cosmology. Specifically, our investigation reveals a substantial disparity in the ellipticities of observed groups with masses \mbox{$10^{13.0}<M_{\rm{h}}<10^{14.5}\ {\rm M_{\odot}}\ h^{-1}$} exhibiting significantly higher ellipticities (at a confidence level of approximately $4\sigma$) compared to their simulated counterparts. Notably, the consistent use of the same group finder for identifying galaxy groups in both observational and simulated datasets underscores the robustness of this result. This observation may imply a potential incongruence between the inferred age of the Universe from observations and the predictions of the model, which aligns with the younger Universe hypothesis suggested by the elevated fraction of observed satellite pairs with correlated line-of-sight relative velocities compared to simulations. Our findings significantly strengthen the plausibility of a younger age for our Universe.