Chemodynamical Ages of Small-Scale Kinematic Structures of the Galactic Disc in the Solar Neighborhood from ~250,000 K and M Dwarfs

Abstract

We combine photometric metallicities with astrometry from Gaia DR3 to examine the chemodynamic structure of ~250,000 K dwarfs in the Solar Neighborhood (SN). In kinematics, we observe ridges/clumps of "kinematic groups", like studies of more massive main-sequence stars. Here we note clear differences in both metallicity and vertical velocity as compared to the surrounding regions in velocity space and hypothesize this is due to differences in mean age. To test this, we develop a method to estimate the age distribution of sub-populations of stars. In this method, we use GALAH data to define probability distributions of W vs. [M/H] in age bins of 2 Gyr and determine optimal age distributions as the best fit weighted sum of these distributions. This process is then validated using the GALAH subset. We estimate the probable age distribution for regions in the kinematic plane, where we find significant sub-structure that is correlated with the kinematic groups. Most notably, we find an age gradient across the Hercules streams that is correlated with birth radius. Finally, we examine the bending and breathing modes as a function of age. From this, we observe potential hints of an increase in the bending amplitude with age, which will require further analysis in order to confirm it. This is one of the first studies to examine these chemodynamics in the SN using primarily low-mass stars and we hope these findings can better constrain dynamical models of the Milky Way due to the increase in resolution the sample size provides.