Multiple kinematical populations in Vela OB2 from Gaia DR1 data
  Recent results using radial-velocity measurements from the Gaia-ESO Survey
have led to the discovery of multiple kinematic populations across the Vela OB2
association. We present here a proper-motion study of the same region. Our aim
is to test whether the radial-velocity populations have a counterpart in
proper-motion space, and if so, how the two sets of kinematical data complement
each other. This work is based on parallaxes and proper motions from the TGAS
catalog, as part of Gaia DR1. Two distinct proper-motion populations are found
dispersed across ~5 degrees (or ~30 pc at their likely distances). Their
detailed correspondence to the radial-velocity populations could not be tested,
because of the paucity of common objects. However, compelling indications are
found that one of the new proper-motion populations consists mostly of members
of the young cluster NGC 2547, and the other is related to the gamma Vel
cluster. Constraints on the age of the two populations, both of which appear to
be only 10-35 Myr old, and their possible mutual interactions within the last
1.5 Myrs, are discussed.
