Optical and Near-Infrared Polarimetry of Highly Reddened Type Ia Supernova 2014J: Peculiar Properties of Dust in M82

TL;DR

This study presents optical and near-infrared polarimetry of SN 2014J in M82, revealing peculiar dust properties that differ from Galactic dust, with implications for understanding interstellar polarization in external galaxies.

Contribution

It provides the first detailed polarimetric analysis of SN 2014J across multiple wavelengths, highlighting unique dust characteristics in M82 compared to the Milky Way.

Findings

Polarization reaches 4.8% in B band and decreases at longer wavelengths.

Polarization peaks at shorter wavelengths than Galactic dust.

Dust in M82 has smaller grain sizes (<0.1 μm) and different wavelength dependence.

Abstract

We presented optical and near-infrared multi-band linear polarimetry of the highly reddened Type Ia SN~2014J appeared in M82. SN~2014J exhibits large polarization at shorter wavelengths, e.g., $4.8$\% in $B$ band, and the polarization decreases rapidly at longer wavelengths, with the position angle of the polarization remaining at approximately $40^{\circ}$ over the observed wavelength range. These polarimetric properties suggest that the observed polarization is likely to be caused predominantly by the interstellar dust within M82. Further analysis shows that the polarization peaks at a wavelengths much shorter than those obtained for the Galactic dust. The wavelength dependence of the polarization can be better described by an inverse power law rather than by Serkowski law for Galactic interstellar polarization. These suggests that the nature of the dust in M82 may be different from that in our Galaxy, with polarizing dust grains having a mean radius of $<0.1\ \mu$m.