New member candidates of Upper Scorpius from Gaia DR1
Merín, B.; Riviere-Marichalar, P.; Wilkinson, S.
Spain
Abstract
Context. Selecting a cluster in proper motion space is an established method for identifying members of a star-forming region. The first data release from Gaia (DR1) provides an extremely large and precise stellar catalogue, which when combined with the Tycho-2 catalogue gives the 2.5 million parallaxes and proper motions contained within the Tycho-Gaia Astrometric Solution (TGAS).
Aims: We aim to identify new member candidates of the nearby Upper Scorpius subgroup of the Scorpius-Centaurus Complex within the TGAS catalogue. In doing so, we also aim to validate the use of a density-based clustering algorithm (DBSCAN) on spatial and kinematic data as a robust member selection method.
Methods: We constructed a method for member selection using a density-based clustering algorithm (DBSCAN) applied over proper motion and distance. We then applied this method to Upper Scorpius and evaluated the results and performance of the method.
Results: We identified 167 member candidates of Upper Scorpius, of which 78 are new, distributed within a 10° radius from its core. These member candidates have a mean distance of 145.6 ± 7.5 pc and a mean proper motion of (-11.4, -23.5) ± (0.7, 0.4) mas yr-1. These values are consistent with measured distances and proper motions of previously identified bona fide members of the Upper Scorpius association.