Infrared polarimetry in the Chamaeleon I dark cloud

Position angles and magnitudes of linear polarization in the H band have been measured for 66 stars embedded in or behind the Chamaeleon I dark cloud. These data are used to demonstrate that the magnetic field permeating the cloud has an ordered structure over the full extent of the dark cloud (∼4 pc), with the magnetic field direction changing smoothly from a position angle of ∼100° in the vicinity of HD 97300 in the north to ∼140° in the vicinity of HD 97048 in the south and west. The elongation of the dark cloud is consistent with collapse preferentially along magnetic field lines. The polarizing efficiency of the cloud decreases with increasing line-of-sight extinction. Cloud members show a larger range in degree of polarization and position angle, which is interpreted as due to anisotropic scattering local to these stars