Global survey of star clusters in the Milky Way III. 139 new open
  clusters at high Galactic latitudes
  An earlier analysis of the Milky Way Star Cluster (MWSC) catalogue revealed
an apparent lack of old (> 1 Gyr) open clusters in the solar neighbourhood (< 1
kpc). To fill this gap we undertook a search for hitherto unknown star
clusters, assuming that the missing old clusters reside at high Galactic
latitudes |b|> 20{\deg}. We were looking for stellar density enhancements using
a star count algorithm on the 2MASS point source catalogue. To increase the
contrast between potential clusters and the field, we applied filters in
colour-magnitude space according to typical colour-magnitude diagrams of nearby
old open clusters. The subsequent comparison with lists of known objects
allowed us to select thus far unknown cluster candidates. For verification they
were processed with the standard pipeline used within the MWSC survey for
computing cluster membership probabilities and for determining structural,
kinematic, and astrophysical parameters. In total we discovered 782 density
enhancements, 522 of which were classified as real objects. Among them 139 are
new open clusters with ages 8.3 < log (t [yr]) < 9.7, distances d < 3 kpc, and
distances from the Galactic plane 0.3 < Z < 1 kpc. This new sample has
increased the total number of known high latitude open clusters by about 150%.
Nevertheless, we still observe a lack of older nearby clusters up to 1 kpc from
the Sun. This volume is expected to still contain about 60 unknown clusters
that probably escaped our detection algorithm, which fails to detect sparse
overdensities with large angular size.
