Assessing the physical reality of Milky Way open cluster candidates

Abstract

We report results on the analysis of eleven new Milky Way open cluster candidates, recently discovered from the detection of stellar overdensities in the Vector Point diagram, by employing extreme deconvolution Gaussian mixture models. We treated these objects as real open clusters and derived their fundamental properties with their associated intrinsic dispersions by exploring the parameter space through the minimization of likelihood functions on generated synthetic colour-magnitude diagrams (CMDs). The intrinsic dispersions of the resulting ages turned out to be much larger than those usually obtained for open clusters. Indeed, they resemble those of ages and metallicities of composite star field populations. We also traced their stellar number density profiles and mass functions, derived their total masses, Jacobi and tidal radii, which helped us as criteria while assessing their physical nature as real open clusters. Because the eleven candidates show a clear gathering of stars in the proper motion plane and some hint for similar distances, we concluded that they are possibly sparse groups of stars.

9 pages, 6 figures. Accepted for publication in MNRAS

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• Improving the open cluster census. III. Using cluster masses, radii, and dynamics to create a cleaned open cluster catalogue
• Survey for Distant Stellar Aggregates in Galactic Disk: Detecting Two Thousand Star Clusters and Candidates, along with the Dwarf Galaxy IC10