Confirmation of line detection in EGSY8p7 over two nights. Left: HST F160W image of the EGSY8p7 field with the slit orientations adopted in two successive nights. Right: extracted 1D signal-to-noise spectra across the J band for each night with a zoom of the 2D data around the line, marked with a vertical blue line. The 2D spectra are smoothed with a 3-pixel Gaussian for better illustration of the data. The 1D spectrum is smoothed with a Gaussian of σ = 5 Å, comparable to the measured line width. The Y axis is scaled so that the peak signal to noise matches the integrated value (e.g., F13). Horizontal dashed lines mark the ﹩\pm 3\sigma ﹩ region. On both nights, the signal to noise at the line location significantly exceeds that elsewhere.