Progenitors of type Ia supernovae and the metallicity distribution of
  G-type dwarfs
  We investigate the contribution to the formation of type Ia supernovae of the
single (a white dwarf accreting from a non-degenerate companion) and double
(two merging white dwarfs) degenerate scenario, as well as various aspects of
the binary evolution process leading to such a progenitor system. We aim to get
a better insight into uncertainties and parameter spaces by means of a combined
modelization, resulting in a reduction of the number of possible model
approaches. This exclusion of parts of the parameter space is, as will be
shown, often independent of uncertainties in the modelization. We use the
combination of a population synthesis code with detailed binary evolution and a
galactic chemical evolution model to predict the metallicity distribution of
G-type dwarfs in the solar neighborhood. Because of the very long lifetime of
these stars, this distribution is a good indicator of the entire chemical
history of a region. By comparing the observed distribution with those
predicted by assuming different type Ia supernova progenitors and evolutionary
parameters (e.g. concerning mass and angular momentum loss and common envelope
evolution), it is possible to constrain the possible combinations of
assumptions. We find that in order to reproduce the observed G-dwarf
metallicity distribution, it is absolutely necessary to include both the single
and double degenerate scenario. The best match is obtained when all merging C-O
white dwarfs contribute to the latter. The correspondence is also critically
dependent on the assumptions about galaxy and star formation, e.g. the use of
the two-infall model vs. a constant star formation rate. However, this does not
affect the previous conclusion, which is consistent with the results obtained
by investigating type Ia supernova delay time distributions in starburst
galaxies.
