Overview of the five targeted systems before subtraction of the unresolved QSO’s PSF and continuum sources (see Sect. 3). Left: integrated spectra of the QSOs and SMGs inside a 3″ radius aperture. Vertical dashed lines indicate the positions of the Lyα and QSO broad lines (Si IV, C IV, HeII, and CIII[[INLINE106]]). The gray shaded region indicates the FWHM of the nebular Lyα emission for the QSOs (see Fig. 2 and Table 3) and the 30 Å narrow band used for the SMGs (see Fig. 3). Right: 30 Å SB maps at the expected Lyα wavelength of the targeted QSOs and SMGs before PSF- and continuum-subtraction (see Sect. 3). The maps have a side of 20″, corresponding to about 129, 152, 148, 133, and 132 kpc for BR1202 − 0725, G09 − 0902 + 0101, G15 − 1444 − 0044, ALESS61.1, and ALESS65.1, respectively.