A Simple Linear Model to Aid in Analyses of the Β Pictoris Moving Group

We build a 4D linear model of object membership in the Pictoris moving group (BPMG), using two nested applications of Principal Component Analysis (PCA) for similar to 1.5 million objects with high-quality data. These data consist of 3D-Galactic space velocities and Gaia G magnitudes. Through PCA, they ultimately result in a 4D straight line, referred to as PC 1 ', about which both the bona fide members used to obtain the straight line and the candidate members used to test the model congregate at generally small distances. As a proof of concept, we select bona fide members from a recent, Gaia DR2-based compilation and candidate members mostly from a (pre-Gaia DR2) compilation from 2017. Using a standard procedure to flag groups of outliers in data sets, we find possible outliers flagged on account of their large distances to PC 1 ', and find evidence that discrepant radial velocity measurements may indeed bring into question their validity as BPMG members. We propose that PC 1 ' be added to the tool set for BPMG analyses and potentially extended to other young stellar moving groups.