IRAS 09002-4732: A Laboratory for the Formation of Rich Stellar Clusters

TL;DR

IRAS 09002-4732 is a young, dense stellar cluster forming within a molecular filament, with a rich population of pre-main sequence stars and active star formation, providing insights into hierarchical cluster formation models.

Contribution

This study presents the first detailed multi-wavelength analysis of IRAS 09002-4732, revealing its rich stellar population, spatial structure, and star formation activity, supporting hierarchical cluster formation theories.

Findings

The cluster has a population twice that of the Orion Nebula Cluster.

Star formation is actively occurring in both the cluster and the filament.

The cluster's initial mass function may lack the most massive stars.

Abstract

IRAS 09002-4732 is a poorly studied embedded cluster of stars in the Vela Molecular Ridge at a distance of 1.7kpc. Deep observations with the Chandra X-ray Observatory, combined with existing optical and infrared surveys, produce a catalog of 441 probable pre-main sequence members of the region. The stellar spatial distribution has two components: most stars reside in a rich, compact, elliptical cluster, but a minority reside within a molecular filament several parsecs long that straddles the cluster. The filament has active distributed star formation with dozens of unclustered protostars. The cluster pre-main sequence population is $\leq 0.8$ Myr old and deeply embedded; its most massive member is extremely young producing an ultracompact H II region. The cluster total population deduced from the X-ray luminosity function is surprisingly rich, twice that of the Orion Nebula Cluster. The cluster core is remarkably dense where strong N-body interactions should be occurring; its Initial Mass Function may be deficient in massive stars. We infer that IRAS 09002-4732 is a rare case where a rich cluster is forming today in a molecular filament, consistent with astrophysical models of cluster formation in clouds that involve the hierarchical formation and merging of groups in molecular filaments.