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 sam pling was done on a locally Cartesian grid with 1 degrees (true angle) spac ing in Galactic longitude and latitude. Of the 11,478 points in the grid, t he 4982 that rise above an elevation of 30 degrees in Cambridge, Massachuse tts, the site of the 1.2 m millimeter-wave telescope used for the survey, w ere 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 n ew and 75 are associated with 26 previously cataloged high-latitude molecul ar 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 no rthern Galactic hemisphere at b greater than or equal to +30 degrees. On th e 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 r egion 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.