Magnetic field structure of the central source in the radio galaxy Virgo A

The properties of the linearly polarized radiation observed in the central source of Vir A (M87) agree with the hypothesis of a large-scale bipolar magnetic field structure for this source. The Faraday rotation measure in the knots of the M87 jet increases systematically with distance from the center, perhaps because interstellar gas is being swept up by expanding, axisymmetric magnetic field loops expelled from the central region of the galaxy