Two waves of massive stars running away from the young cluster R136

TL;DR

This study identifies two distinct mechanisms ejecting massive stars from cluster R136, revealing a higher escape fraction than models predicted, which impacts our understanding of galactic evolution.

Contribution

It uncovers two channels of massive star ejection from R136 and shows models underestimate the escape fraction, highlighting the importance of runaway stars in galactic environments.

Findings

Two ejection channels identified: isotropic and directional.

23-33% of massive stars are runaways.

Model predictions underestimate escape fractions.

Abstract

Massive stars are predominantly born in stellar associations or clusters. Their radiation fields, stellar winds, and supernovae strongly impact their local environment. In the first few million years of a cluster's life, massive stars are dynamically ejected running away from the cluster at high speed. However, the production rate of dynamically ejected runaways is poorly constrained. Here we report on a sample of 55 massive runaway stars ejected from the young cluster R136 in the Large Magellanic Cloud. Astrometric analysis with Gaia reveals two channels of dynamically ejected runaways. The first channel ejects massive stars in all directions and is consistent with dynamical interactions during and after the birth of R136. The second channel launches stars in a preferred direction and may be related to a cluster interaction. We find that 23-33% of the most luminous stars initially born in R136 are runaways. Model predictions have significantly underestimated the dynamical escape fraction of massive stars. Consequently, their role in shaping and heating the interstellar and galactic medium, along with their role in driving galactic outflows, is far more important than previously thought.