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

   FIGURE 2.-Distribution of the linearly polarized emission at 21.1 cm in the
 field of M33 presented as contours in equal steps of 12 mJy per b.a. (1.5
 {sigma}). The zero contour is dashed. Bars show the orientation of the
 measured E-field; their lengths give the degree of linear polarization in the
 range from 5 % to 30 %. Smaller degrees have minimal length; higher values
 have maximal length and are additionally marked by a cross-line. The scale is
 indicated at the top. Three point source positions with possibly polarized
 emission are indicated by << x >> and the source number of tables III and IV.
 The hatched circle symbolizes the antenna beam. 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.