We carried out a spectral line survey of CH3OH toward a large sample of 175 high-mass star-forming regions in the 3mm, 2mm, and 1.3mm bands with the Institut de Radioastronomie Millimetrique (IRAM) 30m telescope. Out of our 175 targets, 148 sources were detected with one or more CH_3_OH transition lines. Nineteen CH_3_OH transition lines, including 13 thermal lines and 6 maser lines, were detected. The 8_0_->7_1_ A^+^ (~95.169GHz) CH_3_OH maser line, one of the strongest class I CH_3_OH maser lines, was detected in 52 sources. Forty-two of them are previously reported masers and the other 10 are new detections. Through analyzing the rotational diagram of the detected CH3OH emission lines (nonmasing lines), we obtained the rotational temperature and the column density for 111 sources. Our results show that E-type CH_3_OH tends to have lower column density than A-type CH_3_OH. The column density ratio of E/A was derived in 55 sources with the majority having a ratio less than 1.0 (about 70%), with a peak ratio of ~0.6. This is consistent with theoretical predictions, i.e., overabundance of A-type CH_3_OH at low temperature leading to a low E/A ratio. Furthermore, we found that CH3OH abundance decreases beyond T_dust_~30K, which is supported by modeling results. All these support the fact that CH3OH is easily formed at low-temperature environments, via successive hydrogenation of CO on cold dust surfaces.

Cone search capability for table J/ApJS/266/29/table3 (Information on detected CH_3_OH transition lines)