| Abstract | The linearly polarized emission of M31 at 2700 MHz is shown to be confined to the prominent optical and H I arms that form a 'ring' at a distance of about 10 kpc from the center, which is elliptical in the plane of the galaxy. The variation of the polarization brightness temperature in the ring suggests that the magnetic field is probably oriented along H I features, some of which deviate considerably from a circle. Another finding is that the sense of the large-scale magnetic field in the ring is the same as that of the rotation of M31. The ratio between the strengths of the uniform and random magnetic fields (for a spatial resolution of 0.9 x 4.2 kpc) is 0.38 + or - 0.03 in the nuclear region, increasing to 0.9 + or - 0.1 in the ring. |
