NED object is 3C 031; Reference is 1996ASPC..100..241L

   Figure 2. The inner jets of 3C31 at 8.4 GHz (resolution 0.7" FWHM). The
 lowest contour level is 35 {mu} Jy per beam area. Vector lengths are
 proportional to the degree of polarization, and 1" corresponds to 50%. The
 vector directions are those of the polarization E-vector. Faraday rotation is
 negligible at this frequency, and the apparent magnetic field is accurately
 orthogonal to the vectors.