New Candidate Massive Clusters from 2MASS
  Massive stars are important for the evolution of the interstellar medium. The
detailed study of their properties (such as mass loss, rotation, magnetic
fields) is enormously facilitated by samples of these objects in young massive
galactic star clusters. Using 2MASS we have searched for so far unknown
candidates of red supergiant clusters along the Galactic Plane. Utilising deep
high resolution UKIDSS GPS and VISTA VVV data to study colour-magnitude
diagrams, we uncover six new massive cluster candidates in the inner Galaxy. If
spectroscopically confirmed as real clusters, two of them could be part of the
Scutum-Complex. One cluster candidate has a number of potential red supergiant
members comparable to RSGC1 and 3.
  Our investigation of UKIDSS data reveals for the first time the main sequence
of the massive cluster RSGC2. The stars of the sequence show an increased
projected density at the same position as the known red supergiants in the
cluster and have E(J-K)=1.6mag. This either indicates an unusual extinction law
along the line of sight or a much lower near infrared extinction to the cluster
than previously estimated in the literature. We suggest that psf-photometry in
UKIDSS images might be able to uncover the main sequence of other RSGC
clusters.
