Initial-final mass relations (IFMRs) for single WDs. The solid white line indicates the IFMR for stars that evolve as isolated single stars. The colours represent the IFMR for single WDs that form as a result of a merger event in a binary at some point during the evolution of the progenitor system. More precisely, the colours logarithmically indicate the 2D probability density function (PDF) obtained from our data through the kernel density estimation method. We plot the initial mass of the initially more massive star against the mass of the single WD formed after the merger event. In this figure, we assume all stars are formed simultaneously 10 Gyr ago, and do not include observational selection effects. The dashed white line is a linear fit (M_WD = 0.128 M_init + 0.435) to the binary merger IFMR, obtained through linear regression of all (M_WD, M_init) points in our data.