NED object is MESSIER 031; Reference is 1969MNRAS.144..101P

   FIG. 5. Contours of the map presented in Fig. 4: the contour interval is 3
 deg K at 408 MHz. Isolated minima are denoted by the symbol <, and regions
 above the 6 deg K and 12 deg K contours, except those near the nucleus, are
 shaded. The symbol x indicates the positions of the brightest discrete sources
 whose responses have been removed; small spurious responses may remain near
 these points.