Layout of the LUCI mask (black square: 4′ × 4′) overlaid on the UltraVISTA K_s-band 6′ × 6′ image. The slits assigned to the spectroscopic targets are shown as red rectangles (1″ × 8–10″) and identified by the slit number, alignment stars are shown by yellow square. The SPIRE sources positions are indicated by blue circles (11″ in radius). Planck red-excess contours (at 50, 62.5, 75 and 87.5% of the highest value) are shown as purple lines. North is up and east to the left.