Development of models for nearby young stellar moving groups: creation, revision, and finalisation of the models

Abstract

Lee & Song (2018, Paper 1) developed a tool for calculating Bayesian membership probability for nearby young stellar moving groups (BAMG: Bayesian Analysis of Moving Groups). The study presented the importance of careful construction of models in moving group membership assessment, using $\beta$ Pictoris moving group as a test case. In this study, we build models for all major nearby young stellar moving groups (NYMGs hereafter) through 4 stages. A set of prototype models is created using members listed in the discovery paper of each group. For each group, suggested members after the discovery of the group are used for revising these prototype models. As these additional members being incorporated, group properties of a NYMG changes, thus membership probabilities change as well. A subset of stars show consistently large membership probabilities regardless of the details of a chosen method for ingesting additional members. Utilising these members, the NYMG models are finalised. The finalised models are applied for evaluating memberships of all claimed candidate members, resulting in a list of bona fide members. The mass function of bona fide members for the entire set of NYMG members indicates that more late-M type members should be identified. In addition, some objects showing a large difference in membership probability between BAMG and BANYAN $\Sigma$ (Gagne et al. 2018b) are presented and discussed. Memberships of some planet host stars are changed, and it can have a significant influence on the estimated planetary masses.