Left panel: [3.6] image of JKCS 041. The field of view is 5 × 5 arcmin, the ruler is 1 arcmin wide. North is up, east to the left. Central panel: color distribution in the cluster line-of-sight (solid red histogram) and in the control field direction (blue dashed histogram). The arrow indicates the expected color of a Grasil young star-forming galaxy (green arrow) at the cluster redshift. Top-right panel: luminosity function. The points marks the LF as usually derived in the astronomical literature, whereas the continuous (blue) curve and the shaded area mark the LF and its 68% errors based on our Bayesian analysis. The fit is performed on unbinned data, not on the binned data plotted in this figure. Bottom-right panel: probability distribution of m^∗. The shortest 68% interval is shaded. The dashed line indicates the assumed prior.