Chemo-kinematics of the Milky Way spiral arms and bar resonances: connection to ridges and moving groups in the Solar vicinity

TL;DR

This study links Milky Way spiral arms and bar resonances to observed stellar ridges and moving groups using N-body simulations and Gaia data, revealing their spatial and kinematic relationships.

Contribution

It introduces a new N-body simulation approach combined with Gaia data to connect spiral arm structures, ridges, and moving groups in the Milky Way.

Findings

Overdensities in angular momentum trace spiral arms and ridges.

Stars near guiding centers form structures matching observed features.

Bar resonances correlate with specific moving groups.

Abstract

Using of a new N-body simulation, as well as Gaia DR2/EDR3 data complemented by data from the Galah, APOGEE, LAMOST surveys, we explore the possible link between the MW spiral arms, RVphi-ridges and moving groups in local UV space. We show that the tightly wound main spiral arms in the N-body model can be successfully identified using overdensities in angular momentum (AM) or guiding space, as well as in the distribution of dynamically cold stars close to their guiding centers. Stars in the AM overdensities that travel over many kpc in radius trace extended density ridges in RVphi space and overdensities in the UV plane of a SNd-like region, similar to those observed in the Gaia data. Similarly, the AM space of the MW contains several overdensities which correlate with a wave-like radial velocity pattern; this pattern is also reproduced by stars well beyond the SNd. We find that the fraction of Gaia stars located near their guiding centers shows three large-scale structures that approximately coincide with the MW spiral arms traced by distributions of maser sources in the Sagittarius, Local, and Perseus arms. Similar to the model, the stars in the AM overdensities follow the main RVphi ridges. When these ridges cross the SNd, they can be matched with the main UV features. Thus we suggest that the Hat is the inner tail of the Perseus arm, one of the Hercules components is the Sagittarius arm and the Arcturus stream is likely to be the outermost tail of the Scutum-Centaurus arm. Based on previous work, the bar corotation is suggested to coincide with the Hercules stream, and the OLR with the Sirius stream. The latter is supported by a sharp decrease of the mean metallicity beyond the Sirius stream, which is an expected behaviour of the OLR. In various phase-space coordinates the AM overdensities stars have systematically higher mean metallicity...(Abridged)