Normalization iterative process to derive the mass model. The local volume density is the sum of the stellar volume mass density of alive stars (derived from the luminosity function and the mass–luminosity relation) and a fraction representing the volume density of remnants . The stellar mass density of each age bin is derived in block A and then applied in Eq. (1) to calculate the mass reservoir. SFR(i) is a vector that stores seven dimensionless factors normalized to unity, reflecting the intensity of the SFR during each age interval.The is the total (all ages) surface density in the solar neighborhood (SN).