NED object is MESSIER 033; Reference is 1987A&AS...68..171B

   FIGURE 9.-Distribution of the linearly polarized emission at 6.3 cm in the
 field of M33 presented as contours in equal steps of 1.1 mJy per b.a. The
 sensitivity in the marked inner part is 0.7 mJy per b.a. Bars show the
 orientations of the measured E-field; their lengths give the degree of
 polarization (see Fig. 2). Three positions of possibly polarized point sources
 are indicated. The coordinate grid is the same in all maps and refers to right
 ascension and declination of 1950.0. The optical centre at {alpha}_50_ =
 1h31m01.67s and {delta}_50_ = 30deg24'15.0" (de Vaucouleurs and Leach, 1981)
 is marked by << + >> in all figures.