A search for southern ultracool dwarfs in young moving groups

Abstract

We associate 132 low-mass ultracool dwarfs in the southern hemisphere as candidate members of five moving groups (MGs) using photometric and astrometric selection techniques. Of these objects, we present high-resolution spectroscopy for seven candidates and combine these with previous measurements from the literature to determine spectral types and radial velocities. We thus constrain distance and space motion spectroscopically, allowing the kinematic membership of the MGs to be assessed. Possible membership of MGs has allowed ages and metallicities to be constrained for these objects and evolutionary models have been used to estimate their mass. We estimate that up to ∼75 of our candidate MG members should be genuine, and discuss future work that will confirm and exploit this major new sample.