The detection of the TRGB in Sculptor. Left: the reddening-corrected CMD of Upper-RGB stars (I ₀ < 18.0 mag) in our IMACS catalog. The cyan lines define the color–magnitude selection used to isolate RGB stars for the TRGB detection. Red dots are foreground sources removed with Gaia EDR3 proper motions. Open black points are member sources excluded by the color cut. Center: the GLOESS-smoothed LF (red, solid) with a smoothing parameter of σ _s = 0.1 and 0.01 mag binned LF (gray). Right: edge response function. The measured TRGB is I ₀ = 15.54 ± 0.07_stat ± 0.02_sys mag.