Massive Protostars and Small Protoclusters

Recent investigations of massive protostellar candidates in the near-infrared (NIR) wavelengths reveal several 2μm visible embedded clusters, NIR counterparts to massive star precursors and H₂ emission in the shape of rings and flared disks around the massive protostars. These observations have shown that in an embedded cluster, the massive stars form one-half to one Myrs after the first generation of low mass stars are born. The H₂ emission in the shape of rings and flared disks represent huge tori of molecular material around massive protostars. These two results in conjunction are consistent with the theory of massive star formation by continuing accretion. The clusters associated with very young precursors to massive stars may represent an evolutionary stage prior to dynamical relaxation. Detailed studies of two clusters reveal flattened, ring shaped morphology both in stellar content and molecular gas. These ring clusters are consistent with the prediction of a theory to form small clusters through fragmentation of magnetically subcritical cloud to multiple magnetically supercritical cores.