Dust Grain Properties in Extragalactic Environment Through Supernovae Dust Polarization Observations

Dust polarization observations of starlight at multi-wavelengths helps us to find maximum polarization, P _max and the corresponding wavelength, λmax . This λmax is approximately proportional to average grain size, thereby helping to reveal grain sizes in the intervening medium. We study the average grain sizes in different host galaxies of 4 Type Ia and 10 Type II supernovae through spectropolarimetric observations at multi-wavelengths and compare with the average grain sizes in the diffused interstellar medium of our galaxy. We use archival P _max, λmax and width of peak of polarization curve (K) values from the literature. We plot P _max versus λmax in color scale that represents K and find that grain sizes of some of the galaxies are smaller, some nearly comparable and some larger than typical grain size (≈5500 Å) of our galaxy. This gives us an insight into the different grain properties especially their sizes in external galaxies compared to our galaxy.