Peter J. Barnes — Page 2

arXiv2008

ATCA and Spitzer Observations of the Binary Protostellar Systems CG30 and BHR71

We present interferometric observations with resolution of ~3 arcsecs of the isolated, low-mass protostellar double cores CG30 and BHR71 in the N2$H+(1-0) line and at 3mm dust continuum, using the Australian Telescope Compact Array (ATCA). The results are complemented by infrared data from the Spitzer Space Telescope. In CG30, the 3mm dust continuum images resolve two compact sources with a separation of ~21.7 arcsecs (~8700 AU). In BHR71, strong dust continuum emission is detected at the position of the mid-infrared source IRS1, while only weak emission is detected from the secondary mid-infrared source IRS2. Assuming optically thin 3mm dust continuum emission, we derive hydrogen gas masses of 0.05--2.1 $M_\odot$ for the four sub-cores. N2H+(1-0) line emission is detected in both CG30 and BHR71, and is spatially associated with the thermal dust continuum emission. We derive the velocity fields and find symmetric velocity gradients in both sources. Assuming that these gradients are due to core rotation, we estimate the specific angular momenta and ratios of rotational energy to gravitational energy for all cores. We also find that the N2H+ emission is strongly affected by the outflows, both in terms of entrainment and molecule destruction. $Spitzer$ images show the mid-infrared emission from all four sub-cores. All four sources appear to drive their own outflows. Based on the ATCA and $Spitzer$ observations, we construct spectral energy distributions (SEDs) and derive temperatures and luminosities for all cores. Based on the morphology and velocity structure, we suggest that the sub-cores in CG30 were formed by initial fragmentation of a filamentary prestellar core, while those in BHR71 could originate from rotational fragmentation of a single collapsing protostellar core.

astro-ph↗

arXiv2005

High-Mass Cloud Cores in the eta Carinae Giant Molecular Cloud

We carried out an unbiased survey for massive dense cores in the giant molecular 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 15 cores are associated with IRAS point sources whose luminosities are larger than 10^4 Lo, which indicates that massive star formation is occuring within these cores. Five cores including the two with IRAS sources are associated with MSX point sources. We detected H13CO+ (1-0) emission toward 4 C18O cores, one of which is associated with neither IRAS nor MSX point sources. This core shows the presence of a bipolar molecular outflow in 12CO (2-1), which indicates that star formation is also occuring in the core. In total, six C18O cores out of 15 are experienced star formation, and at least 2 of 15 are massive-star forming cores in the eta Car GMC. We found that massive star formation occurs preferentially in cores with larger column density, mass, number density, and smaller ratio of virial mass to LTE mass Mvir/M. We also found that the cores in the eta Car GMC are characterized by large line width and Mvir/M on average compared to the cores in other GMCs. We investigated the origin of a large amount of turbulence in the eta Car GMC. We propose the possibility that the large turbulence was pre-existing when the GMC was formed, and is now dissipating. Mechanisms such as multiple supernova explosions in the Carina flare supershell may have contributed to form a GMC with a large amount of turbulence.

astro-ph↗