Gas dynamics in the Milky Way: a low pattern speed model

TL;DR

This paper models the gas dynamics of the Milky Way using hydrodynamical simulations with a low pattern speed bar, successfully reproducing observed features better than previous high pattern speed models.

Contribution

It introduces a low pattern speed model for the Milky Way's bar that aligns well with observed gas flow features, improving upon prior high pattern speed models.

Findings

Reproduces key features in the ($l,v$) diagram

Matches observed kinematics of nuclear ring and spiral arms

Provides a better fit than previous models with higher pattern speeds

Abstract

We present gas flow models for the Milky Way based on high-resolution grid-based hydrodynamical simulations. The basic galactic potential we use is from a N-body model constrained by the density of red clump giants in the Galactic bulge. We augment this potential with a nuclear bulge, two pairs of spiral arms and additional mass at the bar end to represent the long bar component. With this combined model we can reproduce many features in the observed ($l,v$) diagram with a bar pattern speed of $33\; {\rm km}\;{\rm s}^{-1}\;{\rm kpc}^{-1}$ and a spiral pattern speed of $23\; {\rm km}\;{\rm s}^{-1}\;{\rm kpc}^{-1}$. The shape and kinematics of the nuclear ring, Bania's Clump 2, the Connecting arm, the Near and Far 3-kpc arms, the Molecular Ring, and the spiral arm tangent points in our simulations are comparable to those in the observations. Our results imply that a low pattern speed model for the bar in our Milky Way reproduces the observations for a suitable Galactic potential. Our best model gives a better match to the ($l,v$) diagram than previous high pattern speed hydrodynamical simulations.