A $Gaia$ EDR3 search for tidal tails in disintegrating open clusters

TL;DR

This study uses Gaia EDR3 data to identify tidal tails in open clusters, revealing their structure, mass segregation, and potential origins as remnants of massive clusters, enhancing understanding of cluster evolution.

Contribution

The paper introduces a robust method for detecting tidal tails in open clusters and analyzes their mass segregation and evolutionary status using Gaia data.

Findings

46 clusters have stellar corona beyond the tidal radius.

20 clusters exhibit extended tidal tails aligned with their orbit.

Some clusters with initial masses over 10^4 solar masses may be dissolving remnants of young massive 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 $\sim1$ kpc) is the furthest open cluster exhibiting tidal tails that are $\sim50$ pc from its center, while also identifying $\sim40$ 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 ($\rm\lambda_{MSR}$) 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$\rm_{i}$) of these open clusters finding that some of them, having M$\rm_{i}\gtrsim 10^{4} M_{\odot}$, could be the dissolving remnants of Young Massive Clusters.