Catching Galactic open clusters in advanced stages of dynamical
  evolution
  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 $CT_1$
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 $\leq\textrm{log}(t \textrm{yr}^{-1})\leq$ 8.3); ESO 260-7 and
ESO065-7 are of intermediate age (9.2 $\leq\textrm{log}(t
\textrm{yr}^{-1})\leq$ 9.4). All studied OCs are located at similar
Galactocentric distances (R$_{G}\sim6-6.9 $kpc), considering uncertainties,
except for ESO 260-7 ($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}\gtrsim30$) 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.
