Three-component Stackel model of the Galaxy based on the rotation curve from maser data

TL;DR

This paper develops a three-component Stackel model of the Galaxy using maser data to fit the rotation curve, accounting for kinematic inhomogeneities and providing an analytical potential expression for further dynamical modeling.

Contribution

It introduces a new three-component Stackel model fitted to maser data, incorporating velocity dispersions and an analytical potential expression for the Galaxy.

Findings

Model fits the observed rotation curve accurately.

Identifies significant kinematic differences between maser groups.

Provides an analytical form of the Galactic potential.

Abstract

A three-component Stackel model of the Galaxy, including the bulge, disk, and halo, is constructed. Parameter estimates of the potential are obtained as a result of fitting the model rotation curve to azimuthal velocities found from data on trigonometric parallaxes and spatial velocities of masers. The fitting method takes into account the measurement and natural dispersions of azimuthal velocities and uses an algorithm for excluding objects with excessive residuals. In order to obtain more uniform samples, the objects were divided into two groups: masers associated with high-mass star forming regions and masers of other types. A significant kinematic inhomogeneity of these groups was identified and taken into account: the azimuthal velocity dispersion is $\sigma_{0,1}=4.3\pm 0.4$~km\,s$^{-1}$, in the first group and $\sigma_{0,2}=15.2\pm1.3$~km\,s$^{-1}$ in the second. After constructing the model of the Galactic-plane potential, it was generalized to the entire space under the assumption of the existence of a third quadratic integral of motion. When reconstructing the Galactic rotation curve in detail, the used algorithm gives an analytical expression for the Stackel potential, which significantly simplifies the task of constructing the Galaxy's phase density model in the Stackel approximation. In order to make the Stackel model more realistic, one needs to develop methods of direct account of data on the vertical distribution of density in the Galaxy.