Star formation history, double degenerates and Type Ia supernovae in the thin disc

We investigate the relation between the star formation history and the evolution of the double-degenerate (DD) population in the thin disc of the Galaxy, which we assume to have formed 10 Gyr before the present. We introduce the use of star formation contribution functions as a device for evaluating the birth rates, total number and merger rates of DDs. These contribution functions help to demonstrate the relation between star formation history and the current DD population and, in particular, show how the numbers of different types of DD are sensitive to different epochs of star formation. Analysis of the contribution functions given by a quasi-exponentially decline in the star formation rate shows that star formation from 0 to 8 Gyr after thin-disc formation dominates the present rates and total numbers of He+He and CO+He DDs. Similarly, the current numbers of CO+CO and ONeMg+X DDs come mainly from early star formation (