Spectra extracted from the apertures indicated in Fig. 1 and zoomed near the expected wavelength of HeII at the redshift of GN-z11. Specifically, the left panel shows the spectrum extracted from the aperture centred on the ‘HeII clump’ (red box in Fig. 1 and smaller white box in Fig. 3). The right panel shows the spectrum extracted from the larger aperture encompassing the extended HeII emission in the NE quadrant of GN-z11 (yellow box in Fig. 1 and larger white box in Fig. 3). The red vertical bars indicate the expected wavelength of HeII at the redshift of GN-z11, z = 10.603, and the wavelength of the centroid of the line in the clump, which, if identified as HeII, gives a redshift z = 10.600. The dotted lines indicate the noise per spectral pixel in each spectrum inferred from the rms directly measured in the spectrum around the HeII line.