Integrated emission maps of CCS and C₄H towards the sources in our sample. The solid line contours indicate 90 and 50% of the integrated intensity peak with the exception of the C₄H transition in L429, where the contours indicate 90 and 70% of the integrated intensity peak. The dashed line contours represent the A_V values computed from the Herschel/SPIRE maps (5, 10, and 15 mag for B68; 20, 40, and 70 mag for L429; 10, 15, and 20 mag for L1521E; 20, 40, and 80 mag for L694-2; 20, 40, and 60 mag for HMM-1; 20, 30, and 40 mag for OphD). The white circle in the bottom left of each panel shows the 40′′ beam of the SPIRE data.