SN Ia rate as a function of galaxy mass. Black circles are the observed rates in the four mass bins, reported in Table 2, while lines connect the theoretical rates at the median ⟨ Age ⟩ of the distributions in the four mass bins. Solid (red) and dashed (blue) lines refer to exponentially declining SFH models with τ = 0.1 and 8 Gyr, respectively. The shaded areas show the range covered when using the 30th or 70th percentiles of the ⟨ Age ⟩ distribution instead of the median ⟨ Age ⟩, for the exponentially declining SFH models with τ = 0.1 Gyr.