2019ApJS..241...18Y

We report the results of our systematic survey for Galactic 6.7 GHz Class II CH₃OH maser emission toward a sample of young stellar objects. The survey was conducted with the Shanghai Tianma Radio Telescope (TMRT). The sample consists of 3348 sources selected from the all-sky Wide-field Infrared Survey Explorer (WISE) point-source catalog. We discussed the selection criteria in detail and the detection results of those at high Galactic latitudes (i.e., | b| > 2^○) in a previous paper (Yang et al. 2017). Here, we present the results from the survey of those at low Galactic latitudes, i.e., | b| < 2^○. Of 1875 selected WISE point sources, 291 positions that were actually associated with 224 sources that were detected with CH₃OH maser emission. Among them, 32 are newly detected. A majority of the newly detected sources are associated with bright WISE sources. The majority of the detected sources (209/224 = 93.3%) are quite close to the Galactic Plane (| b| < 1^○) and lie on the inner spiral arms with positive local standard of rest velocities. The detection rate and the color-color distribution of our detection are all matched with our anticipation. Combining with detections from previous surveys, we compile a catalog of 1085 sources with 6.7 GHz CH₃OH maser emission in our Galaxy.