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