Catching Galactic open clusters in advanced stages of dynamical evolution

M.S. ANGELO, A.E. PIATTI, W.S. DIAS AND F.F.S. MAIA

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

WILEY-BLACKWELL PUBLISHING, INC

Lugar: Londres; Año: 2018 vol. 477 p. 3600 - 3622

0035-8711

During their dynamical evolution, Galactic open clusters (OCs) gradually losetheir stellar content mainly because of internal relaxation and tidal forces. In thiscontext, the study of dynamically evolved OCs is necessary to properly understandsuch processes. We present a comprehensive Washington CT1 photometric analysis ofsix sparse OCs, namely: ESO518-3, Ruprecht 121, ESO134-12, NGC6573, ESO260-7and ESO065-7.We employed Markov chain Monte-Carlo simulations to robustly deter-mine the central coordinates and the structural parameters and T1 (C 􀀀T1) colour-magnitude diagrams (CMDs) cleaned from eld contamination were used to derivethe fundamental parameters. ESO518-03, Ruprecht 121, ESO134-12 and NGC6573resulted to be of nearly the same young age (8.26 log(t yr􀀀1) 68.3); ESO260-7 andESO065-7 are of intermediate age (9.26 log(t yr􀀀1) 69.4). All studied OCs are lo-cated at similar Galactocentric distances (RG 6􀀀6:9 kpc), considering uncertainties,except for ESO260-7 (RG = 8:9 kpc). These OCs are in a tidally lled regime and aredynamically evolved, since they are much older than their half-mass relaxation times(t=trh & 30) and present signals of low-mass star depletion. We distinguished twogroups: those dynamically evolving towards nal disruptions and those in an advanceddynamical evolutionary stage. Although we do not rule out that the Milky Way poten-tial could have made dierentially faster their dynamical evolutions, we speculate herewith the possibility that they have been mainly driven by initial formation conditions.