A polarimetric study of the reflection nebulae NGC 2068 and NGC 2023 in the Orion R1 association

Abstract

Polarimetry studies of two reflection nebulae in the Orion R1 association are used to determine the nature of the dust in which recently formed stars are embedded in, and show the geometry of the surrounding dust cloud. The data reductions presented are on NGC 2068 and NGC 2023, which are centres of recent low-mass star formation and are embedded on the nearside of LI 630. In the case of NGC 2068, it appears that there is a single illuminating star which illuminates a foreground tilted slab of varying dust density from the rear. A simple tilted slab model assuming single Mie scattering from homogeneous spherical grains was used to fit visual data of traces of polarization, polarized intensity and total intensity through HD 38563N in a north-south direction. The model favoured metallic grains; the best fit being for iron grains and a slab 0.5 parsecs in front of HD 38563N tilted at an angle 55 degrees to the line-of-sight. In the case of NGC 2023, multicolour polarimetry is presented in B,V,R,I and Z. The star HD 37903 was found to be the sole illuminating star. A model to fit the spectral dependence of polarization gave low refractive index grains assuming a power law size distribution. Associated with NGC 2023 are Herbig-Haro objects HH-1, 4, which were found not to be polarized.