A Large-scale CO J = 3-2 Survey of the Galactic Center

Abstract

We have surveyed the central molecular zone (CMZ) of our Galaxy in the CO J = 3-2 line with the Atacama Submillimeter-wave Telescope Experiment (ASTE). Molecular gas in the Galactic center shows high J = 3-2/J = 1-0 intensity ratio (∼ 0.9) while gas in the Galactic disk shows the lower ratio (∼ 0.5). The high-velocity compact cloud CO 0.02-0.02 and the hyperenergetic shell CO 1.27+0.01, as well as gas in the Sgr A region exhibit high J = 3-2/J = 1-0 intensity ratio exceeding 1.5. We also found a number of small spots of high ratio gas. Some of these high ratio spots have large velocity widths and some seem to associate with nonthermal ‘threads’ or filaments. These could be spots of hot molecular gas shocked by unidentified supernovae which may be abundant in the CMZ.