A clustered origin for isolated massive stars

TL;DR

This paper proposes that isolated high-mass stars in the Large Magellanic Cloud originate from dispersed cluster environments due to tidal disruption during cluster mergers, challenging the idea they formed in isolation.

Contribution

It introduces an alternative explanation for isolated massive stars, emphasizing their formation in clusters followed by dispersal through tidal disruption in mergers.

Findings

Simulations predict low-velocity, high-mass stars at >20 pc from clusters.

Cluster mergers can produce halos of young, high-mass stars.

Dispersed stars retain velocities consistent with cluster interactions.

Abstract

High-mass stars are commonly found in stellar clusters promoting the idea that their formation occurs due to the physical processes linked with a young stellar cluster. It has recently been reported that isolated high-mass stars are present in the Large Magellanic Cloud. Due to their low velocities it has been argued that these are high-mass stars which formed without a surrounding stellar cluster. In this paper we present an alternative explanation for the origin of these stars in which they formed in a cluster environment but are subsequently dispersed into the field as their natal cluster is tidally disrupted in a merger with a higher-mass cluster. They escape the merged cluster with relatively low velocities typical of the cluster interaction and thus of the larger scale velocity dispersion, similarly to the observed stars. $N$-body simulations of cluster mergers predict a sizeable population of low velocity ($\le$ 20 km s$^{-1}$), high-mass stars at distances of > 20 pc from the cluster. High-mass clusters in which gas poor mergers are frequent would be expected to commonly have halos of young stars, including high-mass stars, that were actually formed in a cluster environment.