N₂D⁺ column density versus N₂H⁺ column density. Red symbols denote high mass starless cores (HMSCs), high mass protostellar objects (HMPOs), and ultracompact HII regions (UCHIIs) from Fontani et al. (2011), blue circles denote Class 0 objects from Emprechtinger et al. (2009), and green circles denote low mass starless cores from Crapsi et al. (2005). Our sample is indicated with thick black crosses. The two solid black lines indicate D_frac values of 0.26 (average D_frac of the HMSC group) and 0.04 (average D_frac of the HMPO and UCHII groups), similarly to Fig. 1 of Fontani et al. (2011) to aid comparison.