Generalized rotation curves of the Milky Way from the GAIA DR3 data-set: constraints on mass models

Abstract

The circular velocity curve traced by stars provides a direct means of investigating the potential and mass distribution of the Milky Way. Recent measurements of the Galaxy's rotation curve have revealed a significant decrease in velocity for galactic radii larger than approximately 15 kpc. While these determinations have primarily focused on the Galactic plane, the Gaia DR3 data also offer information about off-plane velocity components. By assuming the Milky Way is in a state of Jeans equilibrium, we derived the generalized rotation curve for radial distances spanning from 8.5 kpc to 25 kpc and vertical heights ranging from -2 kpc to 2 kpc. These measurements were employed to constrain the matter distribution using two distinct mass models. The first is the canonical NFW halo model, while the second, the dark matter disk (DMD) model, posits that dark matter is confined to the Galactic plane and follows the distribution of neutral hydrogen. The best-fitting NFW model yields a virial mass of $M_{\text{vir}} = (6.5 \pm 0.5) \times 10^{11} M_\odot$, whereas the DMD model indicates a total mass of $M_{\text{DMD}} = (1.7 \pm 0.2) \times 10^{11} M_\odot$. Our findings indicate that the DMD model generally shows a better fit to both the on-plane and off-plane behaviors at large radial distances of the generalized rotation curves when compared to the NFW model. We emphasize that studying the generalized rotation curves at different vertical heights has the potential to provide better constraints on the geometrical properties of the dark matter distribution.