Dichroic extinction and the infrared polarization of young stellar objects in the L1641 dark cloud

33 young stellar objects (YSOs) in the L1641 dark cloud have been studied using near-infrared polarimetry and imaging. The polarization values were found to correlate with the infrared colour of each source. Point-like sources were found to have a strong wavelength dependence on the polarizations with [P-H/P-K] = 1.4 and [P-J/P-K] = 2.5. The results were compared with the polarization behaviour expected from dichroic extinction, as well as scattering models. Dichroic extinction from aligned dust grains in the circumstellar core most naturally explains the observed polarization in reddened sources, although it is likely that a scattering component dominates in relatively unreddened objects, such as T Tauri stars. There is only a poor alignment of the YSO polarization vectors over the cloud, suggesting that the magnetic field was not dominant in the collapse dynamics of L1641.