Fractality of open clusters in singles, pairs, and groups

Abstract

In this work, we investigate the global structural properties and fractality of 1,876 open clusters (OCs) in different environments, including 1,145 singles, 392 pairs, and 339 groups. We analyze cluster mass, age, size, concentration, and fractal structure using the Q parameter and the fractal dimension fdim, and examine their correlations with key physical parameters. Our results reveal systematic environmental trends: clusters in groups are generally younger, less massive, slightly larger, and less centrally concentrated than those in pairs or singles. Fractality is more pronounced in clusters within pairs and groups, with 44% of group clusters exhibiting fractal substructure compared to 38.5% for pairs and 33.2% for singles. Similarly, median fdim values increase from singles (1.13) to pairs (1.16) to groups (1.25), reflecting greater substructure in denser environments. These findings indicate that both intrinsic cluster properties and environmental context significantly influence cluster evolution. More massive clusters tend to evolve toward centrally concentrated, radially symmetric configurations, while less massive clusters retain fractal features for longer periods. Overall, our study demonstrates that open clusters do not evolve in isolation: interactions with the environment play a critical role in shaping their structural evolution and dynamical state.