Dwarf galaxies in non-local gravity

TL;DR

This study explores a non-local gravity theory as an alternative to dark matter by analyzing dwarf galaxy kinematics, finding it can potentially explain observations without dark matter particles, though some parameter inconsistencies remain.

Contribution

It introduces a specific non-local gravity model and tests its predictions against dwarf galaxy data using Bayesian analysis, offering a novel alternative to dark matter explanations.

Findings

NLG can reproduce dwarf galaxy velocity dispersions without dark matter

Constraints on NLG parameters are consistent with previous studies

Some parameter inconsistencies found in Fornax and Sextans galaxies

Abstract

The nature of dark matter remains one of the most pressing open questions in modern cosmology. Despite extensive experimental efforts, no direct or indirect detection of dark matter particles has been confirmed. This has motivated alternative approaches, including modifications to the underlying theory of gravity. In this work, we investigate the implications of a specific non-local gravity (NLG) theory, which modifies General Relativity by introducing non-local effects that manifest as an effective dark matter component. We analyze the velocity dispersion profiles of eight classical dwarf spheroidal (dSph) galaxies - Carina, Draco, Fornax, Leo I, Leo II, Sculptor, Sextans, and Ursa Minor - to test the predictions of NLG. Using the Jeans equation, we model the kinematics of these galaxies and perform a Bayesian Markov Chain Monte Carlo analysis to constrain the parameters of the NLG kernel chosen for our analysis. Our results indicate that NLG might successfully reproduce the observed kinematics of dSph galaxies without requiring particle dark matter, providing constraints on the scale-dependent modifications to gravity that are compatible with previous studies in the literature. However, a parameter inconsistency remains in the cases of Fornax and Sextans galaxies that requires further attention.