Total number of different spectral stellar types hosting Earthlike planets with minimum habitability conditions (N_★,mHC in Eq. (8)) as a function of Galactic distance and time predicted by the chemical evolution model without stellar migration (model 1; see Section 3.1 and Table 1). The values of (N_★,mHC) are computed within concentric rings of 2 kpc width. Results for M stars are drawn in the upper panel. FGK and retired A are shown in the middle and the lower ones, respectively.