Number density distributions of visible DWDs and the comparison with the observations. The red dots are for the observed samples with determined component masses and the green dots are for those with only minimum companion (dimmer) masses determined (Kruckow et al. 2021). The “brighter” and “dimmer” are defined as the WDs with higher and lower effective temperatures. The catalog of the observed samples is given in appendix Table C.1. Left and right panels are for Ge’s and polytropic models, respectively.