Left panel: mosaic of the entire area observed with MUSE, obtained collapsing the cube information in the 7600−7700 Å wavelength range (“mosaic”), which corresponds to the redshifted Lyα at z ≃ 5.3. We identified six regions characterized by similar background level, the center of the four pointings (P1, P2, P3, P4), the central vertical and horizontal (black rectangles) stripes of overlapping regions. The white square corresponds to the area zoomed in the right panel. Right panel: zoom of the region containing AzTEC-3 (upper red circle) and LBG-1 (lower red circle) in the HST F160W image. We show the position of LBG-3 as black square, the position of LBG-2 (1447523 in Capak et al. 2011 and COSMOS2015_849887 in Laigle et al. 2016) as blue circle, and the position of COSMOS2015_848724 as black circle. These sources are all at z ∼ 5.3. The yellow circle indicates the position of a knot of star formation which can also be part of AzTEC-3. It is worth noting that LBG-1 is located in the center of the mosaic, in the lower corner of the 20 h overlapping region.