Supernovae and their host galaxies - II. The relative frequencies of
  supernovae types in spirals
  We present an analysis of the relative frequencies of different supernova
(SN) types in spirals with various morphologies and in barred or unbarred
galaxies. We use a well-defined and homogeneous sample of spiral host galaxies
of 692 SNe from the Sloan Digital Sky Survey in different stages of
galaxy-galaxy interaction and activity classes of nucleus. We propose that the
underlying mechanisms shaping the number ratios of SNe types can be interpreted
within the framework of interaction-induced star formation, in addition to the
known relations between morphologies and stellar populations. We find a strong
trend in behaviour of the NIa/NCC ratio depending on host morphology, such that
early spirals include more Type Ia SNe. The NIbc/NII ratio is higher in a broad
bin of early-type hosts. The NIa/NCC ratio is nearly constant when changing
from normal, perturbed to interacting galaxies, then declines in merging
galaxies, whereas it jumps to the highest value in post-merging/remnant
galaxies. In contrast, the NIbc/NII ratio jumps to the highest value in merging
galaxies and slightly declines in post-merging/remnant subsample. The
interpretation is that the star formation rates and morphologies of galaxies,
which are strongly affected in the final stages of interaction, have an impact
on the number ratios of SNe types. The NIa/NCC (NIbc/NII) ratio increases
(decreases) from star-forming to active galactic nuclei (AGN) classes of
galaxies. These variations are consistent with the scenario of an
interaction-triggered starburst evolving into AGN during the later stages of
interaction, accompanied with the change of star formation and transformation
of the galaxy morphology into an earlier type.
