High‐Mass Cloud Cores in the η Carinae Giant Molecular Cloud

We carried out an unbiased survey for massive dense cores in the giantmolecular cloud associated with eta Carinae with the NANTEN telescope in 12CO,13CO, and C18O 1-0 emission lines. We identified 15 C18O cores. Two of the 15cores are associated with IRAS point sources whose luminosities are larger than10^4 Lo, which indicates that massive star formation is occuring within thesecores. Five cores including the two with IRAS sources are associated with MSXpoint sources. We detected H13CO+ (1-0) emission toward 4 C18O cores, one ofwhich is associated with neither IRAS nor MSX point sources. This core showsthe presence of a bipolar molecular outflow in 12CO (2-1), which indicates thatstar formation is also occuring in the core. In total, six C18O cores out of 15are experienced star formation, and at least 2 of 15 are massive-star formingcores in the eta Car GMC. We found that massive star formation occurspreferentially in cores with larger column density, mass, number density, andsmaller ratio of virial mass to LTE mass Mvir/M. We also found that the coresin the eta Car GMC are characterized by large line width and Mvir/M on averagecompared to the cores in other GMCs. We investigated the origin of a largeamount of turbulence in the eta Car GMC. We propose the possibility that thelarge turbulence was pre-existing when the GMC was formed, and is nowdissipating. Mechanisms such as multiple supernova explosions in the Carinaflare supershell may have contributed to form a GMC with a large amount ofturbulence.