In this figure, we show the stellar disk masses of DD stars (in lunar masses) of part of the Chen et al. (2014) catalog, as a function of [Fe/H]. Red points are the values of the masses given in the second disk distance model (M_d2) of this catalog. Blue points are the values corresponding to the single distance model (M_d). Green triangles are the DDP stars of Table 1 with M_d values both from Chen’s catalog and the three computed in the current work (see Sect. 3). The green solid line shows the best linear regression (y = ax + b), calculated using a bootstrapping method weighted by the errors on metallicity for all the DDP stars with known M_d – but excluding the HAHM objects that have a different origin than those studied here (see discussion in Sect. 5). The parameter values are shown in the box below the figure. The shaded blue area shows the 68% confidence band of the bootstrapping fit.