2019MNRAS.486.2281D

We examine the molecular content of a large region (∼2200 square degrees) in Pegasus-Pisces with an estimated dark molecular gas fraction of 59 per cent. Using the extensive CO(1-0) Southern Galactic hemisphere, high-latitude survey by Magnani et al. (2000), we re-examined the CO-detectable mass estimates for the region. By averaging all the CO spectra in subsections ranging in size from 3° x 3° to 15° x 15°, we decreased the rms of the averaged CO spectra by factors of 3-10, effectively trading spatial resolution for sensitivity. With the new spectra, we are able to make estimates of the CO-detectable mass as a function of sensitivity. Using the optimal estimate, the CO-detectable mass increases from 2200 to 4000 M_☉, thereby decreasing the dark molecular gas fraction in the region to 0.24. CO(1-0) observations with rms values in the 20-30 mK range can nearly double the molecular mass in regions with diffuse and translucent molecular clouds.