The rotation curve of the Milky Way measured by classical Cepheids from Gaia DR3

Abstract

We determine the rotation curve (RC) of the Milky Way in the range of $6< R < 18\ \rm {kpc}$ using a sample of 903 carefully selected classical Cepheids with precise proper motions and high-quality radial velocities from Gaia Data Release 3. Their distances can be accurately measured from the well-known Period–Wesenheit relations. The RC is computed from the three-dimensional velocities components of these Cepheids. Generally, the RC shows a slight decline with distance from the Galactic centre. On top of this general trend, the newly constructed RC shows a dip around $R\sim 10$–$11\ \rm {kpc}$, followed by a bump around $R\sim 13$–$14\ \rm {kpc}$. This feature has also been reported in other RC measurements, mostly in RCs traced by young tracers like Cepheids. To better constrain the Milky Way mass, an averaged RC is then constructed by combining measurements from this work and previous efforts. Due to the ambiguous nature of the dip-and-bump feature, this averaged RC is constructed only within the radial range where the RC appears to be less influenced by this feature. By using this averaged RC, we determine the circular velocity at solar position and also build a parametrized mass model of our Milky Way. The result for the circular velocity at the solar position is $V_{\mathrm{c}}(R_{0})=236.8\pm 0.8\ \rm {km\ s^{-1}}$, which is in good agreement with previous measurements. The local dark matter density and the enclosed dark matter halo mass within 18 kpc are estimated from the averaged RC under different baryonic models, yielding a series of consistent results: a local density of 0.33–$0.40\ \mathrm{GeV\ cm^{-3}}$ and an enclosed mass of 1.19–$1.45\times 10^{11}\ {\rm M}_{\odot }$.