An imaging polarimetry survey of Type Ia supernovae: are peculiar
  extinction and polarization properties produced by circumstellar or
  interstellar matter?
  Some highly reddened Type Ia supernovae (SNe Ia) display low
total-to-selective extinction ratios ($R_V \lesssim 2$) in comparison to that
of typical Milky Way dust ($R_V \approx 3.3$), and polarization curves that
rise steeply to blue wavelengths, with peak polarization values at short
wavelengths ($\lambda_{\rm max} < 0.4$ ${\mu}$m) in comparison to the typical
Galactic values ($\lambda_{\rm max} \approx 0.55$ ${\mu}$m). Understanding the
source of these properties could provide insight into the progenitor systems of
SNe Ia. We aim to determine whether they are the result of the host galaxy's
interstellar dust or circumstellar dust. This is accomplished by analysing the
continuum polarization of 66 SNe Ia in dust-rich spiral galaxies and 13 SNe Ia
in dust-poor elliptical galaxies as a function of normalised galactocentric
distance. We find that there is a general trend of SNe Ia in spiral galaxies
displaying increased polarization values when located closer to the host
galaxies' centre, while SNe Ia in elliptical host galaxies display low
polarization. Furthermore, all highly polarized SNe Ia in spiral host galaxies
display polarization curves rising toward blue wavelengths, while no evidence
of such polarization properties is shown in elliptical host galaxies. This
indicates that the source of the peculiar polarization curves is likely the
result of interstellar material as opposed to circumstellar material. The
peculiar polarization and extinction properties observed toward some SNe Ia may
be explained by the radiative torque disruption mechanism induced by the SN or
the interstellar radiation field.
