Three Models of the Gravitational Potential of the Milky Way

TL;DR

This work refines the Milky Way's axisymmetric gravitational potential by constructing a smooth rotation curve over $R\in[0,190]$ kpc from a diverse set of tracers, yielding two disk+halo models and a bulge+disk+halo model. The potentials adopt a Plummer bulge, Miyamoto-Nagai disk, and a Navarro-Frenk-White–like halo, with parameters fitted under local density and vertical-force constraints and validated against Illustris TNG50 simulations. Among the models, the three-component bulge+disk+halo (model 3) is the most self-consistent with cosmological analogs, while the two-component models can deviate in the solar neighborhood but still capture the large-scale rotation. The results provide mass profiles and rotation-curve benchmarks that support studies of long-term orbital evolution in the inner Galaxy and enable meaningful comparisons with cosmological galaxy formation scenarios.

Abstract

The parameters of an axisymmetric model for the gravitational potential of the Galaxy have been refined. The basic curve of the Galaxy's rotation in a distance interval of $R:0-190$ kpc was constructed using the velocities of masers, classical Cepheids, Red Clump stars, Blue Horizontal Branch stars, halo stars, globular clusters, and dwarf satellite galaxies of the Milky Way. The rotation curve was selected in such a way that there would be no dominant burst of circular velocities in the central ($R<2$ kpc) region of the Galaxy. As a result, we constructed two two-component models of the galactic potential, which include contributions from the disk and the halo of invisible matter, as well as a three-component model with a small-mass bulge added in advance. These models can be useful in studying the long-term orbital evolution of stars and open and globular star clusters in the central ($R<4$ kpc) region of the Galaxy. The constructed models were tested for self-consistency by comparing their rotation curves with a set of model curves generated with the Illustris TNG50 software package.

Figures (5)

• Figure 1: The rotation curve of the Galaxy for model 2-1 (orange thick line); the vertical line marks the position of the Sun; the thin black lines indicate the contributions of the disk and the halo; the velocities of classical Cepheids, masers with measured trigonometric parallaxes, and high-luminosity red giants [37] are shown with blue squares, red circles, and green triangles, respectively, while the gray circles show the velocities according to [1].
• Figure 2: Segments of the rotation curves of the Galaxy in the solar neighborhood, which were found in the studies listed in the legend, in comparison to the rotation curve based on model 2-1; LRGB is the luminous red giant branch.
• Figure 3: The rotation curves of the Galaxy corresponding to models 2-1 and 2-2.
• Figure 4: The rotation curve of the Galaxy for model 3 (thick orange line), the vertical line marks the position of the Sun, the thin black lines indicate the contributions of a bulge, a disk, and a halo; the velocities of classical Cepheids, masers with measured trigonometric parallaxes, and high-luminosity red giants [37] are shown with blue squares, red circles, and green triangles, respectively, while the gray circles show the velocities according to [1].
• Figure 5: The rotation curves according to models 2-2 and 3 (solid lines) compared to their counterparts from the TNG50 cosmological simulations (dashed lines). The inset shows the face-on images of model galaxies according to simulations in the region from $-$15 kpc to 15 kpc relative to the disk center.