THE GALAXY CLUSTER MID-INFRARED LUMINOSITY FUNCTION AT 1.3 < z < 3.2

We present 4.5 [mu]m luminosity functions for galaxies identified in 178 candidate galaxy clusters at 1.3 < z < 3.2. We find that [alpha] = -1 describes the luminosity function very well in all redshift bins and does not evolve significantly. We find a slight trend toward fainter m* for the richest clusters, implying that the most massive clusters in our sample could contain older stellar populations, yet another example of cosmic downsizing. This value, found from our targeted survey, is significantly lower than the values found for slightly lower redshift, z ~ 1, clusters found in wide-field surveys. The results are consistent with cosmic downsizing, as the clusters studied here were all found in the vicinity of RLAGNs-which have proven to be preferentially located in massive dark matter halos in the richest environments at high redshift-and they may therefore be older and more evolved systems than the general protocluster population.