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

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.