An optical and near-infrared polarization survey of nearby starburst and interacting galaxies

Abstract

Broadband optical and near-infrared polarization and flux density measurements of a sample of 27 starburst and interacting galaxies are presented. The observed polarizations are generally small (P is less than 1 percent) and decrease with increasing wavelength. For those galaxies with significant polarization, the polarization E vector is usually parallel to a dust lane. The most likely polarization mechanism is the transmission of radiation through aligned dust grains lying in the plane of the galaxy. In some cases scattering by dust grains may contribute to the polarization. NGC 253 shows high polarization (4.3 percent in the V band), with a strong wavelength-dependence resembling a Serkowski curve having a small value of lambda(max) (0.34 micron). Modeling shows that this wavelength-dependence can also be produced by light polarized according to the Serkowski formula with a normal value of lambda(max) (0.55 micron) combined with unpolarized light with a redder spectrum.