Chemodynamical signatures of bar resonances in the Galactic disk: current data and future prospects

TL;DR

This paper investigates the chemical and dynamical signatures of the Galactic bar's resonances using simulations and recent stellar survey data, highlighting current limitations and future prospects for identifying these features.

Contribution

It introduces a method to distinguish bar resonance signatures in the Milky Way using chemodynamical data and compares simulations with Gaia and LAMOST observations.

Findings

Weak evidence for a slow bar from the 'hat' moving group.

Stars closer to the bar's minor axis show stronger resonance signatures.

Future data will improve the identification of bar resonances.

Abstract

The Galactic disk exhibits complex chemical and dynamical substructure thought to be induced by the bar, spiral arms, and satellites. Here, we explore the chemical signatures of bar resonances in action and velocity space and characterize the differences between the signatures of corotation and higher-order resonances using test particle simulations. Thanks to recent surveys, we now have large datasets containing metallicities and kinematics of stars outside the solar neighborhood. We compare the simulations to the observational data from Gaia EDR3 and LAMOST DR5 and find weak evidence for a slow bar with the "hat" moving group ($250~\text{km/s} \lesssim v_\phi \lesssim 270~\text{km/s}$) associated with its outer Lindblad resonance and "Hercules" ($170~\textrm{km/s} \lesssim v_\phi \lesssim 195~\text{km/s}$) with corotation. While constraints from current data are limited by their spatial footprint, stars closer in azimuth than the Sun to the bar's minor axis show much stronger signatures of the bar's outer Lindblad and corotation resonances in test particle simulations. Future datasets with greater azimuthal coverage, including the final Gaia data release, will allow reliable chemodynamical identification of bar resonances.