New Candidate Massive Clusters from 2MASS

TL;DR

This paper reports the discovery of six new massive star cluster candidates in the inner Galaxy using 2MASS, UKIDSS, and VISTA data, with potential implications for understanding red supergiants and cluster properties.

Contribution

It introduces new candidate massive clusters identified through infrared surveys and reveals the main sequence of RSGC2 for the first time, suggesting new methods for cluster detection.

Findings

Six new massive cluster candidates identified.

Main sequence of RSGC2 revealed for the first time.

Potential link of some clusters to the Scutum-Complex.

Abstract

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.