BANYAN. XIII. A First Look at Nearby Young Associations with Gaia Data Release 2

Abstract In this paper, we examine the nearest 100 pc entries in Data Release 2 of Gaia to identify previously unrecognized candidate members in young associations. We analyze 695 952 stars with the BANYAN Σ Bayesian classification software and discover 898 new high-likelihood candidate members that span a wide range of properties, from spectral types B9 to L2, including 104 comoving systems, 111 brown dwarfs, and 31 new bona fide members. Our sample is mostly composed of highly active M dwarfs and will be crucial in examining the low-mass end of the initial mass function of young associations. Our sample includes new candidate members near the Galactic plane where previous surveys suffered from a high rate of contamination. This paper represents the first step toward a full reassessment of young associations in the solar neighborhood with the second data release of the Gaia mission.