A Gaia EDR3 search for tidal tails in disintegrating open clusters

Abstract

We carry out a search for tidal tails in a sample of open clusters with known relatively elongated morphology. We identify the member stars of these clusters from the precise astrometric and deep photometric data from Gaia Early Data Release 3 using the robust membership determination algorithm, ML-MOC. We identify 46 open clusters having a stellar corona beyond the tidal radius, 20 of which exhibit extended tails aligned with the cluster orbit direction in Galactocentric coordinates. Notably, we find NGC 6940 (at a distance of ∼1 kpc) is the furthest open cluster, exhibiting tidal tails that are ∼50 pc from its centre, while also identifying ∼40 pc long tidal tails for the nearby Pleiades. Using the minimum spanning tree length for the most massive stars relative to all cluster members, we obtain the mass segregation ratio (⁠⁠) profiles as a function of the number of massive stars in each cluster. From these profiles, we can classify the open clusters into four classes based on the degree of mass segregation experienced by the clusters. We find that clusters in the most mass segregated classes are the oldest on average and have the flattest mass function slope. Of the 46 open clusters studied in this work, 41 exhibit some degree of mass segregation. Furthermore, we estimate the initial masses (M⁠) of these open clusters, finding that some of them, having M⁠, could be the dissolving remnants of young massive clusters.