A survey of high-latitude molecular gas in the southern Galactic hemisphere

To determine the distribution of molecular gas at high Galactic latitudes, nearly one-half of the southern Galactic hemisphere at b less than or equal to -30 degrees was surveyed in the CO (1-0) transition at 115 GHz. The sampling was done on a locally Cartesian grid with 1 degrees (true angle) spacing in Galactic longitude and latitude. Of the 11,478 points in the grid, the 4982 that rise above an elevation of 30 degrees in Cambridge, Massachusetts, the site of the 1.2 m millimeter-wave telescope used for the survey, were observed to an rms of T-A* similar to 0.1 K. We found 144 distinct CO (1-0) emission lines along 133 lines of sight. Of these detections, 58 are new and 75 are associated with 26 previously cataloged high-latitude molecular clouds situated within the survey boundaries. The surface filling factor of molecular gas is 0.03, a factor of 10 greater than that found in the northern Galactic hemisphere at b greater than or equal to +30 degrees. On the assumption that the CO/H-2 ratio [N(H-2)/W(CO)] is given by 1.0 x 10(20) cm(-2) (K km s(-1))(-1), the mass surface density of molecular gas in the region of the survey is 0.09 M. pc(-2). The Gaussian scale height of the 133 detections is similar to 100 pc, consistent with that determined for lower latitude dark clouds.