Degree of polarization of Z CMa. North is up, east is left. The black and green lines show the trajectories of the large jet and micro-jet, respectively. The green cross shows the position of the binary; the separation of the stars is smaller than the size of the symbol. Left: P_Θ is shown by the vectors. Only regions of the image with an S/N higher than 3 are displayed in this image. The length of the vectors is proportional to the local degree of polarization. Right: P image smoothed by convolution with a Gaussian kernel of 5 pixels. The black contours indicate the regions of the image where P is higher than 1.5%. The three arrows indicate the three regions of the image discussed in Sect. 4.