X-Shooter NIR spectrum of the HZ1 galaxy. Top panel shows the combined, rebinned (∼ 85 km s⁻¹), and smoothed (0.7 nm × 0.12 ″) 2D spectrum. The bottom three panels illustrate the extracted 1D spectra rebinned by ∼ 210 km s⁻¹, ∼ 170 km s⁻¹, and ∼ 140 km s⁻¹, respectively. Expected positions of the [CIII]λ1907 at λ = 1276.9 nm and CIII]λ1909 line at λ = 1275.6 nm, based on the Lyα spectroscopic redshift, are shown as yellow and red lines, respectively. Shaded blue regions indicate the flux, dotted lines indicate the uncertainties, whereas the orange solid line is the best Gaussian fit.