WISE and Herschel sources on WISE 12 μm (left) and Herschel 250 μm (right) brightness maps. From the WISE PSC, only sources classified as Class I, Class II, shocked H₂ gas, and resolved PAH emission according to the Koenig et al. (2012) criteria are shown. For Herschel sources the symbols are as in Fig. 6. Herschel sources classified as protostellar but presenting no association with a WISE protostar were classified from submillimetre data (see Sect. 4.4.1).