Catching Galactic open clusters in advanced stages of dynamical evolution

Abstract

During their dynamical evolution, Galactic open clusters (OCs) gradually lose their stellar content mainly because of internal relaxation and tidal forces. In this context, the study of dynamically evolved OCs is necessary to properly understand such processes. We present a comprehensive Washington $C{T}_1$ photometric analysis of six sparse OCs, namely: ESO 518-3, Ruprecht 121, ESO 134-12, NGC 6573, ESO 260-7 and ESO 065-7. We employed Markov chain Monte-Carlo simulations to robustly determine the central coordinates and the structural parameters and $T_1\times (C-T_1)$ colour-magnitude diagrams (CMDs) cleaned from field contamination were used to derive the fundamental parameters. ESO 518-03, Ruprecht 121, ESO 134-12 and NGC 6573 resulted to be of nearly the same young age (8.2 $\le \text{log}(t{\text{yr}}^{-1})\le$ 8.3); ESO 260-7 and ESO065-7 are of intermediate age (9.2 $\le \text{log}(t{\text{yr}}^{-1})\le$ 9.4). All studied OCs are located at similar Galactocentric distances (R${}_G\sim 6-6.9$kpc), considering uncertainties, except for ESO 260-7 ($R_G=8.9$kpc). These OCs are in a tidally filled regime and are dynamically evolved, since they are much older than their half-mass relaxation times ($t/t_{rh}\gtrsim 30$) and present signals of low-mass star depletion. We distinguished two groups: those dynamically evolving towards final disruptions and those in an advanced dynamical evolutionary stage. Although we do not rule out that the Milky Way potential could have made differentially faster their dynamical evolutions, we speculate here with the possibility that they have been mainly driven by initial formation conditions.

24 pages, 24 figures

References in corpus (9)

• The Gaia mission
• A new generation of PARSEC-COLIBRI stellar isochrones including the TP-AGB phase
• Lifetimes of tidally limited star clusters with different radii
• The Size of Star Clusters Accreted by the Milky Way
• Highly dynamically evolved intermediate-age open clusters
• Observational hints of a real age spread in the young LMC star cluster NGC 1971
• Gemini/GMOS photometry of intermediate-age star clusters in the Large Magellanic Cloud
• A comprehensive photometric study of dynamically evolved small van den Bergh-Hagen open clusters
• On the physical reality of overlooked open clusters

Cited by in corpus (9)

• Clusters and mirages: cataloguing stellar aggregates in the Milky Way
• A Multi-Band Catalog of 10978 Star Clusters, Associations and Candidates in the Milky Way
• Three new Galactic star clusters discovered in the field of the open cluster NGC 5999 with Gaia DR2
• The Quintuplet Cluster: Extended Structure and Tidal Radius
• Nearly coeval intermediate-age Milky Way star clusters at very different dynamics evolutionary stages
• Characterizing dynamical stages of open clusters located in the Sagittarius spiral arm
• Study of the Open Clusters in Kepler Prime Field
• The VISCACHA survey -- VIII. Chemical evolution history of Small Magellanic Cloud West Halo cluster
• Dynamical Evolution of The Open Clusters Collinder 110 and NGC 2477