Year: 2026
Type: article
Abstract: We derive both the midplane and off-plane rotation curves, v c ( R , z ), and the vertical acceleration, a z ( R , z ), of the Milky Way (MW) using Gaia third data release over the ranges of vertical heights z ∈ (−2,2) kpc and galactocentric distances R ∈ (8.5, 14) kpc where the velocity components are determined with high precision, i.e., with an error <5%. In contrast, the vertical acceleration a z ( R , z ) is dominated by model-dependent systematics, with uncertainties of up to ∼20%. This level of accuracy allows us to place stringent constraints on the geometry of the MW’s dark matter (DM) distribution, since the vertical gradients of the gravitational potential attain their maximum within this range of radial and vertical distances corresponding to the characteristic scales of the disk. We find that models including the observed stellar components together with a spherical DM halo fail to reproduce both the pronounced variation of v c ( R , z ) with height and the observed behavior of a z ( R , z ). In particular, spherical halos with a scale radius of r s ∼ 15 kpc contribute negligibly to the off-plane rotation curve and vertical acceleration in the inner disk, leaving these features primarily determined by the stellar mass distribution. Conversely, models in which DM is confined to a flattened, disk-like configuration predict substantial contributions to both v c ( R , z ) and a z ( R , z ), resulting in a markedly better agreement with the data. We conclude that disk-like DM distributions are strongly favored over spherical halo models. Forthcoming Gaia data releases will enable even more stringent tests of the geometry and distribution of the MW’s DM component.
Source: The Astrophysical Journal
Institutions: Centro Ricerche Enrico Fermi, Sapienza University of Rome
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
Funder: European Space Agency
OpenAlex ID: W7167642894