Encounters in the ONC - observing imprints of star-disc interactions

TL;DR

This study combines observations and simulations to investigate how star-disc interactions in the Orion Nebula Cluster lead to high-velocity stars and disc destruction, revealing the impact of close encounters on young star dynamics.

Contribution

It provides a detailed analysis linking high-velocity stars to close three-body encounters and disc destruction, supported by observational data and numerical simulations.

Findings

8 to 18 stars leave the ONC with velocities several times the velocity dispersion.

High-velocity stars are mainly young low-mass stars, some lacking infrared excess.

High-velocity stars are concentrated in two regions of the ONC, correlating with encounter locations.

Abstract

The external destruction of protoplanetary discs in a clustered environment acts mainly due to two mechanisms: gravitational drag by stellar encounters and evaporation by strong stellar winds and radiation. If encounters play a role in disc destruction, one would expect that stars devoid of disc material would show unexpectedly high velocities as an outcome of close interactions. We want to quantify this effect by numerical simulations and compare it to observations. As a model cluster we chose the Orion Nebula Cluster (ONC). We found from the observational data that 8 to 18 stars leave the ONC with velocities several times the velocity dispersion. The majority of these high-velocity stars are young low-mass stars, among them several lacking infrared excess emission. Interestingly, the high-velocity stars are found only in two separate regions of the ONC. Our simulations give an explanation for the location of the high-velocity stars and provide evidence for a strong correlation between location and disc destruction. The high-velocity stars can be explained as the outcome of close three-body encounters; the partial lack of disc signatures is attributed to gravitational interaction. The spatial distribution of the high-velocity stars reflects the initial structure and dynamics of the ONC. Our approach can be generalized to study the evolution of other young dense star clusters, like the Arches cluster, back in time.