Dynamical Evolution of The Open Clusters Collinder 110 and NGC 2477

Abstract

Using Gaia DR3 photometric and astrometric data, we identified the likely members of the open clusters Collinder 110 and NGC 2477, and derived their astrophysical and dynamical parameters. We obtained reddening values of $E(B-V) = 0.43 \pm 0.05$ and $0.33 \pm 0.04$, and ages of $1.82 \pm 0.10$ Gyr and $1.05 \pm 0.10$ Gyr for Collinder 110 and NGC 2477, respectively. Within the uncertainties, the distances derived from the color-magnitude diagrams ($2.09 \pm 0.06$ and $1.38 \pm 0.04$ kpc) are consistent with those obtained from Gaia DR3 parallaxes ($2.08 \pm 0.31$ and $1.45 \pm 0.11$ kpc). Both clusters exhibit large core and limiting radii. The core radius ($R_c$) of Collinder 110 does not follow the expected decreasing trend with increasing evolutionary parameter ($\logτ_2$). In addition to losing part of its low-mass stellar content, its relatively large $R_c$ may reflect primordial conditions and/or the presence of a possible stellar-mass black hole. The relatively large $R_c/R_h$ ratios, together with their advanced dynamical evolution ($\logτ_2 = 1.24$ and $1.34$), indicate that significant two-body relaxation and mass segregation have occurred within their central regions. The small values of $R_h/R_j$ ($0.32$ and $0.16$) suggest that low-mass stars have dynamically redistributed within the comparatively large Jacobi radii under the combined influence of internal and external processes. However, their large $R_t/R_j$ ratios ($1.60$ and $1.23$) imply that both clusters are tidally affected and have likely lost part of their low-mass stellar populations to the Galactic field. Despite these effects, their locations in the third Galactic quadrant, where giant molecular clouds are relatively scarce, may explain their survival to their present ages of $1.82$ and $1.05$ Gyr, respectively.