A High-Latitude Molecular Structure in Pegasus-Pisces

Abstract

We detected CO emission from a shell-like or ringlike dust structure approximately 20° across centered near Galactic coordinates (l = 105°, b = -45°). This region was also observed in CO by Yamamoto et al. A total of 106 positions along the ridge of the feature were observed in the CO(1-0) and (2-1) transitions with the Arizona Radio Observatory 12 m millimeter-wave radio telescope at Kitt Peak, Arizona. Emission was detected from 65 lines of sight, plus three with two distinct velocity components. Although the dust emission shows a marked ringlike morphology, the kinematic information from the CO spectra is more ambiguous. The best χ2 fits for two models, an expanding spherical shell and an expanding ring of molecular gas embedded in a sheet of neutral gas, suggest that, at best, only part of the CO emission is associated with an expanding structure. The remaining CO detections are projected onto a stream of neutral hydrogen where CO unrelated to the shell may also have formed. However, if at least part of the CO emission is associated with an expanding shell or ring of molecular gas, the structure has an expansion velocity of 3.8 km s-1, a molecular mass of 1200-1300 M⊙, and an age of ~1 × 107 yr.