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) = 1.6 mag. 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.