Low-mass members of nearby young stellar moving groups from Gaia EDR3

Abstract

Gaia EDR3 offers greatly improved kinematics for nearby objects, including members of nearby young stellar moving groups (NYMGs). In this study, we aim to identify low-mass NYMG members (spectral types of M0 to mid-L) in Gaia EDR3. We calculated spatio-kinematic membership probabilities by utilizing a Bayesian membership probability calculation scheme developed in our previous study. We evaluated stellar youth primarily based on colour-magnitude diagram positions. Combining spatio-kinematic membership assessment and youth evaluation, we identified ~2900 low-mass NYMG candidate members, including ~700 previously claimed members. In the set of ~2200 new candidate members, ~550 appear to be young based on NUV brightness. Our pilot spectroscopic study with Wide Field Spectrograph (WiFeS) on the ANU 2.3-m telescope observed 78 candidates, with 79 per cent confirmed as members. Using our new member sample, we estimated an isochronal age of the β Pictoris Moving Group. The mean age (~10 Myr), which is around half the age of recent estimates, suggests either a truly younger age of the β Pictoris Moving Group or inaccuracies in contemporary isochrones. As the main results of this study, we provide lists of newly confirmed and candidate low-mass NYMG members.