AST/RO 13 CO( J = 2→1) and 12 CO( J = 4→3) Mapping of Southern Spitzer c2d Small Clouds and Cores

Abstract

Forty molecular cloud cores in the southern hemisphere from the initial Spitzer Space Telescope Cores-to-Disks (c2d) Legacy program source list have been surveyed in 13CO(2→1), 12CO(4→3), and 12CO(7→6) with the Antarctic Submillimeter Telescope and Remote Observatory (AST/RO). The cores, 10 of which contain embedded sources, are located mostly in the Vela, Ophiuchus, Lupus, Chamaeleon, Musca, and Scorpius complexes. 12CO(7→6) emission was undetected in all 40 clouds. We present data of 40 sources in 13CO(2→1) and 12CO(4→3), significant upper limits of 12CO(7→6), as well as a statistical analysis of the observed properties of the clouds. We find the typical 13CO(2→1) line width to be 2.0 km s-1 for cores with embedded stars and 1.8 km s-1 for all others. The typical 12CO(4→3) line width is 2.6-3.7 km s-1 for cores with known embedded sources, and 1.6-2.3 km s-1 for all others. The average 13CO column density derived from the line intensities was found to be 1.9 × 1015 cm-2 for cores with embedded stars and 1.5 × 1015 cm-2 for all others. The average kinetic temperature in the molecular cores, determined through a large velocity gradient analysis of a set of nine cores, has an average lower limit of 16 K and an average upper limit of 26 K. The average molecular hydrogen density has an average lower limit of 10 2.9 cm-3 and an average upper limit of 103.3 cm-3 for all cores. For a different subset of nine cores, we have derived masses. They range from 4 to 255 M☉. Overall, our c2d sample of southern molecular cores has a range of properties (line width, column density, size, mass, embedded stars) similar to those of past studies.