Reference map with source labels, corresponding to the numbers in Col. 1 of Table A.1 (in the format “serps##”). Contours and magenta boxes are the same as in Fig. 1, and boxes correspond to regions shown in Fig. 2 in zoom. We simplify the color and marker scheme from Figs. 1 and 2. Here, black indicates a mm source, and gray indicates an IR source with no mm source counterpart. Circle sizes of the markers are not significant, but are smaller in the crowded regions where a zoom version with labels is shown in Fig. 2.