The role of low-mass star clusters in massive star formation in Orion

TL;DR

This study uses deep X-ray observations to analyze the distribution and density of low-mass stars in Orion's massive star-forming regions, supporting the idea that low-mass star clusters play a crucial role in massive star formation.

Contribution

It provides new observational evidence linking low-mass star clustering with massive star formation, emphasizing the importance of dense gas and low-mass clusters in the process.

Findings

Low-mass stars cluster around massive star-forming regions in Orion.

Derived stellar densities reach up to 10^6 stars per cubic parsec.

Supports a model of massive star formation involving dense gas and low-mass star clusters.

Abstract

To distinguish between the different theories proposed to explain massive star formation, it is crucial to establish the distribution, the extinction, and the density of low-mass stars in massive star-forming regions. We analyzed deep X-ray observations of the Orion massive star-forming region using the Chandra Orion Ultradeep Project (COUP) catalog. We found that pre-main sequence (PMS) low-mass stars cluster toward the three massive star-forming regions: the Trapezium Cluster (TC), the Orion Hot Core (OHC), and OMC1-S. We derived low-mass stellar densities of 10^{5} stars pc^{-3} in the TC and OMC1-S, and of 10^{6} stars pc^{-3} in the OHC. The close association between the low-mass star clusters with massive star cradles supports the role of these clusters in the formation of massive stars. The X-ray observations show for the first time in the TC that low-mass stars with intermediate extinction are clustered toward the position of the most massive star, which is surrounded by a ring of non-extincted low-mass stars. Our analysis suggests that at least two basic ingredients are needed in massive star formation: the presence of dense gas and a cluster of low-mass stars. The scenario that better explains our findings assumes high fragmentation in the parental core, accretion at subcore scales that forms a low-mass stellar cluster, and subsequent competitive accretion.