The Main Sequence of three Red Supergiant Clusters

Abstract

Massive clusters in our Galaxy are an ideal testbed to investigate the properties and evolution of high mass stars. They provide statistically significant samples of massive stars of uniform ages. To accurately determine the intrinsic physical properties of these stars we need to establish the distances, ages and reddening of the clusters. One avenue to achieve this is the identification and characterisation of the main sequence members of red supergiant rich clusters. Here we utilise publicly available data from the UKIDSS galactic plane survey. We show that point spread function photometry in conjunction with standard photometric decontamination techniques allows us to identify the most likely main sequence members in the 10-20Myr old clusters RSGC1, 2, and 3. We confirm the previous detection of the main sequence in RSGC2 and provide the first main sequence detection in RSGC1 and RSGC3. There are in excess of 100 stars with more than 8Msun identified in each cluster. These main sequence members are concentrated towards the spectroscopically confirmed red supergiant stars. We utilise the J-K colours of the bright main sequence stars to determine the K-band extinction towards the clusters. The differential reddening is three times as large in the youngest cluster RSGC1 compared to the two older clusters RSGC2 and RSGC3. Spectroscopic follow up of the cluster main sequence stars should lead to more precise distance and age estimates for these clusters as well as the determination of the stellar mass function in these high mass environments.

8pages, 2tables, 2figures, Accepted for publication in MNRAS, full version which includes the complete appendix can be found at http://astro.kent.ac.uk/~df/

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• The Initial Masses of the Red Supergiant Progenitors to Type-II Supernovae
• Properties of Star Clusters - II: Scale Height Evolution of Clusters
• JWST's PEARLS: a new lens model for ACT-CL J0102$-$4915, "EL Gordo'', and the first red supergiant star at cosmological distances discovered by JWST
• The Massive Star-Forming Regions Omnibus X-Ray Catalog, Second Installment
• Diffuse gamma-ray emission from the vicinity of young massive star cluster RSGC 1
• Prospects for Multimessenger Observations of Thorne-Żytkow Objects