The Milky Way bar potential constrained by the kinematics of SiO maser stars in BAaDE Survey

TL;DR

This paper introduces a new method using the longitude-velocity envelope to better constrain the Milky Way's bar potential by comparing test particle simulations with SiO maser star observations from the BAaDE survey.

Contribution

The study demonstrates that the l-v envelope offers more comprehensive constraints on the Galactic bar potential than previous methods, and evaluates different potential models against observational data.

Findings

The l-v envelope aligns reasonably with observed SiO maser stars, with minor discrepancies near the Galactic center.

The P17 potential model suggests a lower central rotation curve and larger quadrupole strength.

The H24 potential does not fully resolve existing issues and may underestimate the central bar mass.

Abstract

We introduce a novel method that utilizes the longitude-velocity (l-v) envelope to constrain the Milky Way (MW) bar potential. Previous work (Habing 2016) used the l-v diagram to explain the distribution of the observed high-velocity stars. We successfully reproduce their results, but find that their method is limited to only one single type of periodic orbits. In contrast, we propose that the l-v envelope provides much more comprehensive constraints. We compare the properties of test particles in the Portai et al. (2017) MW potential model (P17) with the observed SiO maser stars from the Bulge Asymmetries and Dynamical Evolution (BAaDE) survey. We find that the l-v envelope generated by the bar potential demonstrates reasonable agreement with the observational data, albeit with slight discrepancies near the Galactic center. The inconsistencies suggest that the P17 potential yields a lower central rotation curve, a slightly larger quadrupole strength, or a possibly underestimated pattern speed. We also adopt an updated version of the P17 potential with a modified central mass component (CMC) proposed by Hunter et al. (2024) (H24). The fitting of the l-v envelope suggests that the H24 potential does not completely address the existing challenges and may hint at a possible underestimation of the central bar mass. Our study demonstrates that the l-v envelope can be used as a valuable tool for constraining the Galactic potential and provides insights into the Milky Way bar potential.