Correlations between 6.7 GHz integrated flux density and beam-averaged H₂ column density (left), between 6.7 GHz luminosity and mass (middle), and between 6.7 GHz luminosity and H₂ volume density (right) of the associated 1.1 mm BGPS sources in the log-log plot. The dotted line in each panel represents the least-squares fit result to all data points. The correlation coefficient is also marked in each plot. Properties of the 6.7 GHz methanol masers are based on both this current survey and the literature (e.g., Caswell et al. 2010; Green et al. 2010; Szymczak et al. 2012), which are indicated by filled and open circles, respectively.