New member candidates of Upper Scorpius from Gaia DR1
  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 the DBSCAN clustering algorithm 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$^{\circ}$ radius from its core. These
member candidates have a mean distance of 145.6 $\pm$ 7.5 pc, and a mean proper
motion of (-11.4, -23.5) $\pm$ (0.7, 0.4) mas/yr. These values are consistent
with measured distances and proper motions of previously identified bona-fide
members of the Upper Scorpius association.
