POLARIMETRIC EVIDENCE AGAINST A COLLIMATED OUTFLOW IN THE HORSEHEAD NEBULA

Imaging polarimetry of the Horsehead Nebula in Orion shows that the 'jaw' region of the nebula, which includes a proposed collimated flow from a highly reddened star B33-6 (Reipurth & Bouchet) is illuminated by a distant source, σ Orionis, and not by B33-6. The polarization pattern also shows features which suggest the presence of magnetically aligned dust grains in the surrounding medium. The possible structure of the aligning field is discussed. © 1985 Royal Astronomical Society.