NTT follow-up observations of star cluster candidates from the FSR catalogue

Abstract

We are conducting a large program to classify newly discovered Milky Way star cluster candidates from the list of Froebrich et al. Here, we present deep near-infrared (NIR) follow-up observations from European Southern Observatory–New Technology Telescope (ESO/NTT) of 14 star cluster candidates. We show that the combined analysis of star density maps (SDMs) and colour–colour/magnitude diagrams derived from deep NIR imaging is a viable tool to reliably classify new stellar clusters. This allowed us to identify two young clusters with massive stars, three intermediate age open clusters and two globular cluster candidates among our targets. The remaining seven objects are unlikely to be stellar clusters. Among them is the object FSR 1767 which has previously been identified as a globular cluster using Two-Micron All-Sky Survey (2MASS) data by Bonatto et al. Our new analysis shows that FSR 1767 is not a star cluster. We also summarize the currently available follow-up analysis of the FSR candidates and conclude that this catalogue may contain a large number of new stellar clusters, probably dominated by old open clusters.