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

Abstract

Making use of a new high-resolution spiral galaxy simulation as well as Gaia DR2 and EDR3 data complemented by chemical abundances from the Galah DR3, APOGEE DR16, and LAMOST DR5 surveys, we explore the possible link between the Milky Way (MW) spiral arms, (R, vϕ) ridges, and moving groups in local vR-vϕ space. We show that the tightly wound main spiral arms in the N-body simulation can be successfully identified using overdensities in angular momentum (AM) or guiding space and also in the distribution of dynamically cold stars close to their guiding centres. Stars in the AM overdensities that travel over many kiloparsec in radius trace extended density ridges in (R, vϕ) space and overdensities in the vR-vϕ plane of a solar neighbourhood (SNd)-like region, similar to those observed in the Gaia data. Similarly, the AM space of the MW contains several overdensities that 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 centres 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. This approach does not work for the Scutum arm near the end of the bar. Similar to the simulation, the stars in the AM overdensities follow the main (R, vϕ) density ridges with nearly constant angular momentum. When these ridges cross the SNd, they can be matched with the main vR-vϕ 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 second, vϕ ≈ −55 km s−1 Hercules stream ridge, and the OLR with the Sirius stream. The latter is supported by a sharp decrease in mean metallicity beyond the Sirius stream, which is an expected behaviour of the OLR, limiting migration of the metal-rich stars from the inner MW. In various phase-space coordinates, the AM overdensity stars have a mean metallicity that is systematically higher by about 0.05 dex than the metallicity of the surrounding stars. This is a predicted behaviour of the spiral arms. We show that the wave-like metallicity pattern can be traced at least up to |z|≈1 kpc. It is linked to radial velocity variations seen even farther (|z|≈2 kpc) from the Galactic mid-plane.

Chemodynamical Signatures of Bar Resonances in the Galactic Disk: Current Data and Future Prospects

“…For example, a bar with significant deceleration will trap stars with a different distribution of orbits show that metallicity should decrease from the center of the CR resonance to its boundary. N-body models with selfconsistent bars could also provide a richer picture, including the possibly confounding effects of spiral arms, which impact metallicity distributions, and can overlap with bar resonances (e.g., Khoperskov & Gerhard 2022;Asano et al 2022). Stellar ages and chemical abundances beyond [Fe/H] provide additional clues to a star's birth location and, given a better understanding of the Galaxy's chemical evolution, can doubtlessly further constrain birth radius.…”

The LMC impact on the kinematics of the Milky Way satellites: clues from the running solar apex

“…The latest allows us to trace the details of the kinematic response of the halo populations on the first infall of the LMC. The simulations were run using our parallel version of the -code (Fukushige et al 2005;Khoperskov et al 2014) with multithread usage under the SSE and AVX instructions providing us with a good performance and high-precision solutions of similar problems (Saburova et al 2018;Khoperskov et al 2020;Khoperskov & Gerhard 2022). For the time integration, we used a leapfrog scheme with a fixed step size of 0.1 Myr.…”

Spiral-like features in the disc revealed by Gaia DR3 radial actions

“…The orbital parameters and actions computed for this work are available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (130.79.128.5) or via https://cdsarc.cds.unistra.fr/ viz-bin/cat/J/A+A/670/L7 (Palicio et al 2020), ridges in projected velocities (Ramos et al 2018;Fragkoudi et al 2019;Khoperskov & Gerhard 2022;Gaia Collaboration 2022b,a;McMillan et al 2022), distribution of actions (Hunt et al 2019;Sellwood et al 2019;Bland-Hawthorn et al 2019;Trick et al 2019Trick et al , 2021Trick 2022), and distribution of metallicity (Poggio et al 2022). In this work, we report on structures in the Galactic plane revealed by the distribution of the radial action, J R , computed with the Gaia DR3 astrometry and LoS velocities (Gaia Collaboration 2022c).…”