Exploring Milky Way rotation curves with Gaia DR3: a comparison between $\Lambda$CDM, MOND, and General Relativistic approaches

TL;DR

This study compares various gravitational models, including MOND, $ m f extLambda$CDM, and General Relativity, in fitting the Milky Way's rotation curve using Gaia DR3 data, revealing statistical equivalence but differing dark matter estimates.

Contribution

It extends previous work by incorporating Gaia DR3 data to evaluate and compare the accuracy of multiple gravitational models for the Milky Way's rotation curve.

Findings

All models fit the data statistically equally well.

$ m f extLambda$CDM estimates higher dark matter content than NFW profile.

Non-Newtonian effects dominate beyond 10-15 kpc.

Abstract

With the release of Gaia DR3, we extend the comparison between dynamical models for the Milky Way rotation curve initiated in the previous work. Utilising astrometric and spectro-photometric data for 719143 young disc stars within $|z|<1$ kpc and up to $R \simeq 19$ kpc, we investigate the accuracy of MOND and $\Lambda$CDM frameworks in addition to previously studied models, such as the classical one with a Navarro-Frenk-White dark matter halo and a general relativistic model. We find that all models, including MOND and $\Lambda$CDM, are statistically equivalent in representing the observed rotational velocities. However, $\Lambda$CDM, characterized by an Einasto density profile and cosmological constraints on its parameters, assigns more dark matter than the model featuring a Navarro-Frenk-White profile, with the virial mass estimated at $1.5\text{-}2.5 \times 10^{12} \, {\rm M}_{\odot}$ - a value significantly higher than recent literature estimates. Beyond $10\text{-}15$ kpc, non-Newtonian/non-baryonic contributions to the rotation curve are found to become dominant for all models consistently. Our results suggest the need for further exploration into the role of General Relativity, dark matter, and alternative theories of gravitational dynamics in shaping Milky Way's rotation curve.