H imaging polarimetry of the protoplanetary nebula M2-9

Abstract

After correction for interstellar polarization, our Hα polarization map of the protoplanetary nebula M2-9 shows that a significant fraction of the emission-line radiation from the nebular lobes is scattered radiation originating in the central core. We find no evidence for a spatially extended illuminating source on scales of ≥ 1-2 arcsec. In order to explain our polarization results, we present a geometrical model for the system which has diametrically opposed cavities previously created in a pre-existing dusty envelope. The illumination of the cavity walls leads to the reflection nebula properties of M2-9. We find that the high-excitation emission-line knots, supposedly undergoing regular rotation about the major axis on a time-scale of decades, have not moved significantly since 1977