Finding the dispersing siblings of young open clusters

Dynamical traceback simulations using Gaia DR3^⋆

¹ Lund Observatory, Division of Astrophysics, Department of Physics, Lund University, Box 43, 22100 Lund, Sweden
e-mail: eero.vaher@fysik.lu.se
² School of Physics & Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
³ European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The Netherlands

Received: 11 May 2023
Accepted: 15 September 2023

Abstract

Context. Stars tend to form in clusters, but many escape their birth clusters very early. Identifying the escaped members of clusters can inform us about the dissolution of star clusters, but also about the stellar dynamics in the galaxy. Methods capable of finding escaped stars from many clusters are required to fully exploit the large amounts of data in the Gaia era.

Aims. We present a new method of identifying escaped members of nearby clusters and apply it to ten young clusters.

Methods. We assumed the escaped stars were close to the cluster in the past and performed traceback computations based on the Gaia DR3 radial velocity subsample. For each individual star, our method produces a probability estimate that it is an escaped member of a cluster, and for each cluster it also estimates the field star contamination rate of the identified fugitives.

Results. Our method is capable of finding fugitives that have escaped from their cluster in the last few ten million years. In many cases the fugitives form an elongated structure that covers a large volume.

Conclusions. The results presented here show that traceback computations using Gaia DR3 data can identify stars that have recently escaped their cluster. Our method will be even more useful when applied to future Gaia data releases that contain more radial velocity measurements.