Ten Gyr time-integrated number of SNIa per unit stellar mass formed for the fiducial SNIa model calculated according to Eqs. (13)–(16). The fiducial SNIa model assumes a constant overall SNIa realisation parameter and the gwIMF as given by the IGIMF theory (Eq. (12)) as a function of the galaxy-wide SFR, , and metallicity, [Z/X]. The black line is the relation for [Z/X] = 0. Other lines with different colours represent different values of [Z/X], as indicated by the white stripes on the colour map on the right: [Z/X] = 0.3, 0.2, 0.1, −0.1, −0.2, −0.3, −0.4, −0.5, −1, −2, −4, and −6. The black horizontal dotted line represents the canonical n_Ia(t = 10 Gyr, ξ_canonical) value of 0.0022/M_⊙ (Maoz & Mannucci 2012). The green and red horizontal dashed lines indicate observational constraints on the n_Ia(t = 10 Gyr) for SNIa surveys up to a certain redshift and in galaxy clusters, respectively. The shaded regions represent the uncertainty ranges of the horizontal dashed lines. References are given in Table 1.