NGC 2548: clumpy spatial and kinematic structure in an intermediate-age
  galactic cluster
  NGC 2548 is a 400-500 Myr old open cluster with evidence of spatial
substructures likely caused by its interaction with the Galactic disk. In this
work we use precise astrometric data from the Carte du Ciel - San Fernando
(CdC-SF) catalogue to study the clumpy structure in this cluster. We confirm
the fragmented structure of NGC 2548 but, additionally, the relatively high
precision of our kinematic data lead us to the first detection of substructures
in the proper motion space of a stellar cluster. There are three spatially
separated cores each of which has its own counterpart in the proper motion
distribution. The two main cores lie nearly parallel to the Galactic plane
whereas the third one is significantly fainter than the others and it moves
toward the Galactic plane separating from the rest of the cluster. We derive
core positions and proper motions, as well as the stars belonging to each core.
