Description of source "M17" from Gomez et al. (2010)

The M17 region hosts, among other features, the cometary UC HII region UC-1 (e.g., Felli et al. 1980; Johnson et al. 1998). Distances reported for the M17 nebula have ranged from 2.2 kpc (Chini et al. 1980) to 1.3 kpc (Hanson et al. 1997). More recently, a distance of 1.6 kpc has been reported by Nielbock et al. (2001), which we adopt here.

Unlike the previous two sources, M17 presents very limited 44 GHz maser activity with only a single maser component detected in the field, at a projected distance of 0.2 pc from the UC HII region (see Fig. 3). The maser properties are listed in Table 2; the 19.1 kms−1 velocity that we find is the same as found by KHV04.