for a given DTD would be rather straightforward. For example, using a DTD for each galaxy of the form $$\phi(\Delta t) = \phi_* \, \Delta t_{\rm Gyr}^{-\gamma}\,,
\label{dtd}$$ with $t_{\rm Gyr}=t/$(1 Gyr), and assuming that the entire galactic stellar mass, $M_g$, arose at a single time, $t_g$, in Eq. (\[eq:rate\]) would lead to a galactic specific SN Ia rate at time $t$ of $$\frac{\dot{N}_g(t)}{M_g} = \phi(t_{\rm Gyr}-t_{g,\,{\rm Gyr}}) = \frac{\phi_*}{(t_{\rm Gyr}-t_{g,\,{\rm Gyr}})^\gamma}\,.
\label{grate}$$ This description is incomplete, though. First, the SN Ia rate at present reflects the galactic mass at the time of formation, as opposed to that measured today after stellar mass loss has occurred. We correct for this using the results of @Bruzual:2003tq for a Chabrier IMF (as used in the SDSS galaxy sample) by including a term of the form $M(t_g)/M(t)$.

Additionally, the ages are more accurately galactic averages, so that an assumption of instantaneous formation at $t_g$ will not properly reflect the effect of a DTD. To allow for a finite duration of star formation, we use a declining history of the form $e^{-t/\tau}$, with $\tau = 1$ Gyr, occurring since the time $t_g$ for each galaxy. We further make use of the 16/84% ranges in 