Spectroscopic detection of emission in EGSY8p7 with MOSFIRE. Upper panel: the 2D spectrum below which we plot the raw (black line) and smoothed (blue line) 1D spectrum and its error (faint red shading). The red line shows an example best-fit model of the data (Section 3). Vertical lines mark OH skyline positions. Upper left panel: shows a normalized signal map extracted along the slit within a 5-pixel (﹩\simeq 6.5﹩ Å) wide box centered on the line. The pattern of two negative peaks bracketing the positive peak exactly matches that expected from the dithering scheme used. Arrows show the predicted locations of other lines for a lower-redshift interpretation of the line. Green boxes on the 2D spectrum mark the skyline region typically masked out in our calculations. See Section 3 for more details.