Clockwise from top left: spatial correlation between total intensity, PF, and PI in W3(OH), W3 Main, and S 106 displayed over Herschel SPIRE 250 µm image. Black contours represent 1/PF with levels 0.25, 0.5, 1, 1.5, and 2 (for W3(OH) and W3 Main, top) and 0.1, 0.3, 0.6, and 0.9 (for S 106, bottom). White contours display PI with levels from 20 to 90 mJy/beam in intervals of 10 mJy/beam for W3(OH) and W3 Main (top), and levels 5, 10, 20, 30, 40, 50, and 60 mJy/beam for S 106 (bottom). The cyan vectors in the top two panels mark bipolar patterns in PI that correspond to outflows (see Sect. 5.2). The blue vector in W3 Main identifies the low PF elongated structure centred on IRS 5. This is similar to the elongated disc structure in W3(OH) traced by 1/PF contours.