Total intensity I, polarization intensity PI, and polarization angle PA images of the W4 superbubble at λ6 cm (upper panels a), b), c)), λ11 cm (middle panels d), e), f)), and λ21 cm (bottom panels g), h), i)). The angular resolutions are 95 for λ6 cm images in panels a) and b), 43 for λ11 cm images in panels d) and e), and 935 for λ21 cm images in panels g), h), and i). The PA images at λ6 cm (panel c)) and λ11 cm (panel f)) have angular resolutions of 12′ and 6′, respectively. The total intensity contours for I and PI images run from 1.8 mK T_b in steps of 2.4 mK T_b for λ6 cm, from 10.0 mK T_b in steps of 12.0 mK T_b for λ11 cm (after subtracting strong point-like sources), and from 2000 mK T_b in steps of 50 mK T_b for λ21 cm. The PI contours on the PA images start from 5.0 mK T_b in steps of 1.0 mK T_b for λ6 cm, and from 50.0 mK T_b in steps of 8.0 mK T_b for λ11 cm. PI contours are not overlaid on the λ21 cm PA image, because no clear correlations can be found. The rectangles in panel a) are the regions for TT-plots study, while the rectangles in panels b), c), and e), f) indicate the regions used for the Faraday screen model fitting.