Galaxy rotation curve based on RGB stars from the Gaia DR3 catalogue

TL;DR

The paper presents a model-minimized, data-driven reconstruction of the Milky Way's rotation curve out to approximately 20 kpc by applying the radial Jeans equation in cylindrical coordinates to a Gaia DR3 RGB star sample. It derives $V_{ m c}(R,z)$ from directly measured kinematics, correcting for measurement errors and using an exponential tracer density to express the Jeans terms, while explicitly characterizing azimuthal and vertical variations. The analysis yields a local circular velocity at the Sun of $V_{ m c}(R_\odot)=229.63\pm0.30$ km s$^{-1}$ with $dV_{ m c}/dR=-2.29\pm0.05$ km s$^{-1}$ kpc$^{-1}$ and identifies dips near $R\sim13$ and 18 kpc, indicating a complex velocity field and highlighting the azimuthal dependence of $V_{ m c}$. These results provide a high-resolution, Gaia-only perspective on the Milky Way's mass distribution while emphasizing the limitations of global axisymmetric inferences from a limited azimuthal sampling. The work offers fine-grained rotation-curve information suitable for MW analog studies and cross-galaxy comparisons, and underscores the need to account for azimuthal structure in dynamical modeling.

Abstract

In this paper, we construct a detailed circular velocity curve of the Milky Way out to 20 kpc based on the radial component of the Jeans equation in cylindrical coordinates, assuming an axisymmetric gravitational potential, and show its dependence on azimuth. We use only Gaia DR3 data and aim to minimize the use of model data and various assumptions. To build the rotation curves, we used a sample of 4,547,980 RGB stars with measured spatial velocities, covering the Galactic plane in the range of Galactocentric cylindrical coordinates $150^\circ < θ< 210^\circ$ and 0 < R < 20 kpc. We exclude systematics in the data that may arise from neglecting higher-order moments of the velocity distribution and their dispersions, as well as due to random measurement errors in Gaia. At the distance of the Sun, the circular velocity $V_{\rm c}(R_0)$ turned out to be ($229.63\pm0.30$) km s$^{-1}$, which is in good agreement with many previous estimates. The average slope of the circular velocity is $(-2.29\pm0.05)$ km s$^{-1}$ kpc$^{-1}$ obtained in the range of $R$ from 6 to 20 kpc and $θ$ from 150 to 210 degrees. The determined circular velocity curve has some peculiarities in behavior near $R\sim$13 and 18 kpc, but in general it does not contradict the results of other authors up to distances where our statistics are reliable.

Figures (10)

• Figure 1: The link between the Galactocentric, Galactic and local coordinate systems.
• Figure 2: The centroid velocity component $V_R$ as a function of Galactocentric coordinates.
• Figure 3: The centroid velocity component $V_\Theta$ as a function of Galactocentric coordinates.
• Figure 4: The centroid velocity component $V_Z$ as a function of Galactocentric coordinates.
• Figure 5: $\sigma\varv_R, \sigma\varv_\Theta, \sigma\varv_Z$ and $\sigma\varv_R\varv_Z$ as functions of Galactocentric coordinates.