Sensitive CO(1-0) survey in Pegasus-Pisces reduces CO-dark gas inventory by a factor of 2.

We conducted high-sensitivity, high-velocity resolution CO(1-0) observations in a region containing a portion of the diffuse molecular cloud MBM 53 to determine whether weak CO emission was present. The results of our observations increase the amount of CO-detectable molecular gas in the region by a factor of 2. The increased molecular mass for the cloud, if applicable to the molecular clouds in the entire Pegasus-Pisces region, decreases the dark molecular gas content from 58 per cent of the total H2 mass to ~30 per cent. If the results for MBM53 are applicable to other diffuse clouds, then the fraction of dark gas directly detectable via sensitive CO(1-0) observations in diffuse molecular clouds is similar to that predicted by models for giant molecular clouds. [ABSTRACT FROM AUTHOR]