Infrared imaging polarimetry of galaxies

We have successfully made 1.65 and 2.2 μm polarization maps of four external galaxies at a high level of precision. The disk of NGC 4565 polarizes light at H at a level consistent with interstellar polarization observed in the Milky Way. The polarization in the disk of NGC 891 lies close to, but not exactly in the plane of the galaxy and the polarization is weak for the amount of reddening. We hypothesize that either the lines of sight deep into the disk of NGC 891 pass through alternating regions of torroidal and vertical magnetic fields, or that the magnetic field in this galaxy is highly turbulent on small scales compared to the Milky Way. In the inner disks of these two galaxies scattering polarization does not appear to be a significant contributor at IR wavelengths. The infrared luminous galaxy UGC 2238 has very unusual polarization with a 90° change in position angle from H to K on the nucleus. This behavior can be explained by a combination of a torroidal field in the disk and a poloidal field in the nucleus. Such geometries may be a general characteristic of very luminous galacitc nuclei. Imaging polarimetry of the interacting system Arp 299 confirms and extends the single aperture observations. Polarimetry of IC 694, the more luminous galaxy in the Arp 299 system, suggests a massive polar flow from the nucleus that pulls the magnetic field into a poloidal geometry.