Description of source "G28.83-0.25" from Towner et al. (2017)

We detect two weak 1.3 cm continuum sources (<0.4 mJy beam−1; Table 4) coincident with this EGO. The eastern centimeter source, CM2, is also coincident with compact MIPSGAL 24 μm emission and 6.7 GHz CH3OH masers (Cyganowski et al. 2009). The 1.3 cm emission from this source is spatially extended E–W, with a morphology consistent with multiple unresolved or marginally resolved sources (Figure 1). The western centimeter source, CM1, is unresolved and located ∼4″ west of CM2. Both CM1 and CM2 were detected by Cyganowski et al. (2011a) at 3.6 cm (but not at 1.3 cm; their 1.3 cm 4σ upper limit was 0.92 mJy beam−1).

Interestingly, at 3.6 cm, the western source (CM1 in both papers) is the brighter of the two, while at 1.3 cm, CM2 is the brighter source (Table 4 and Cyganowski et al. 2011a). This reversal suggests that CM2 either has a steeper free–free SED or more contribution from dust than CM1. We do not detect any 25 GHz CH3OH emission above the 4σ level for this EGO.

In at least three of the four CH3OH lines there is, however, very weak emission (~3s; so not included in our analysis), likely thermal, coincident with CM2.