Description of source "g4" from Chambers et al. (2011)

Sources g1, g2, and g4 (Figures 3, 4, and 5) are all coincident with the positions of known PNe (Van de Steene & Jacoby 2001; Jacoby & Van de Steene 2004), are in close proximity to one another, and are isolated from other star formation regions. All three sources are associated with 24 µm emission, but show no correlation with other observational signatures of star formation, such as IRDCs or CH3OH maser emission. Because they are likely to be PNe rather than protostars, we exclude them from our statistical analysis.