Dust grain properties in extragalactic environment through supernovae dust polarisation observations

Abstract

Dust polarisation observations of starlight at multi-wavelengths helps us to find maximum polari6 sation, Pmax and the corresponding wavelength, λmax. This λmax is approximately proportional to 7 average grain size, thereby helping to reveal grain sizes in the intervening medium. We study the 8 average grain sizes in different host galaxies of 4 Type Ia and 10 Type II supernovae through spec9 tropolarimetric observations at multi wavelengths and compare with the average grain sizes in the 10 diffused interstellar medium of our galaxy. We use archival Pmax, λmax and width of peak of polari11 sation curve (K) values from the literature. We plot Pmax versus λmax in color scale that represents 12 K and find that grain sizes of some of the galaxies are smaller, some nearly comparable and some 13 larger than typical grain size (≈ 5500˚A) of our galaxy. This gives us an insight into the different grain 14 properties especially their sizes in external galaxies compared to our galaxy.