Notes. (1) Source names, which are also its Galactic coordinates. If one source has multiple velocity components, letters “a, b, c ...” are used to label them. (2) Systemic velocity of the ¹³CO (1 − 0) lines.(3) Systemic velocity of the maser sources, which are taken from Pestalozzi et al. (2005). (4) Speculation about whether the CO gas is associated with the CH₃OH maser. The letter “q” stands for “questionable” (if the velocity difference between the maser source and the line is in the range from 5 to 10 km s^-1, see Sect. 3.1). (5) Kinematic distances of the maser sources. For the sources with an ambiguity, both solutions (near and far distances) are presented. If there are previous observational results helping to determine the distance, the reference number is given in square brackets. The recommended distance value is labeled with an asterisk. (6) Other distance measurement. (7) Distance value adopted for this paper.(8) Galactocentric distance.(9) Full-width half-maximum (FWHM) line width of the ¹³CO (1 − 0) line component from Gaussian fitting.(10) Excitation temperature of the ¹²CO (1 − 0). (11) H₂ column density, which is derived from the ¹³CO (1 − 0) line emission.

Reference. The indications for the reference numbers in Cols. (5) and (6) are: [a1] Urquhart et al. (2011); [a2] Anderson & Bania (2009); [b1] Kuchar & Bania (1994); [b2] Roman-Duval et al. (2009); [b3] Matthews et al. (2009); [b4] Pandian et al. (2008); [c1] Peretto & Fuller (2009); [c2] Ragan et al. (2012); [c3] Simon et al. (2006); [c4] He et al. (2012); [d1] Faúndez et al. (2004); [e1] Zavagno et al. (2002); [e2] Gwinn et al. (1992); [e3] Blitz et al. (1982); [e4] Xu et al. (2011); [e5] Sato et al. (2010); [e6] Russeil et al. (2007); [e7] Yang et al. (1991); [e8] Arzoumanian et al. (1994). The references are organized into five group according to the different features or procedures used to determine the distance (Sect. 3.3): [a1] and [a2]: 21-cm HI absorption towards background (UC) Hii regions; [b1] to [b4]: 21-cm HI emission and self absorption; [c1] to [c4]: infrared absorption features; [d1]: an indication that the adopted distance should make the source closer to a spiral arm; [e1] to [e8]: other distance measurements besides the kinematical method.