Formation process of young stellar population in Messier 16 from a kinematic perspective

TL;DR

This study uses Gaia data and spectra to analyze the kinematics of young stars in M16, revealing multiple formation mechanisms including cluster expansion, spontaneous formation, and feedback-driven processes.

Contribution

It provides a detailed kinematic analysis of young stars in M16, highlighting the roles of different star formation processes and the cluster's dynamic behavior.

Findings

The distance to M16 is about 1.7 kpc.

The cluster NGC 6611 shows expansion and rotation.

Some stars are associated with gas pillars and likely formed via feedback.

Abstract

We present a kinematic study of young stars in Messier 16 (M16) using the Gaia Data Release 3 and high-resolution spectra. A total of 345 stars are selected as genuine members using the published lists of X-ray, infrared sources, and early-type stars as well as the Gaia data. There is severe differential reddening across this region and the reddening law of the intracluster medium appears abnormal. The distance to M16, derived from the parallaxes of the members, is about 1.7 kpc. The ages of members, estimated by comparing their color-magnitude diagram with theoretical isochrones, range from 1 Myr to 4 Myr. This star-forming region is composed of an open cluster (NGC 6611) and a distributed population. This cluster shows a clear pattern of expansion and rotation. Some of the distributed population are spatially associated with the gas pillars located at the ridge of H II bubble. In particular, several stars moving away from the cluster are physically associated with the northeastern pillar. In addition, their younger ages support the idea that the formation of these stars was triggered by the feedback from massive stars in NGC 6611. On the other hand, the other stars do not show systematic radial or stream motions; therefore, they likely formed through spontaneous star formation events. We discuss the formation of young stars in the context of cluster expansion, spontaneous star formation, and feedback-driven star formation, and suggest that all of these mechanisms possibly contributed to their formation.