Which Came First, The Cluster or the Early-Type Galaxy?

The association between galaxy clusters and early-type galaxies has existed for more than half the history of the Universe, and both stellar mass and environment are known to be correlated with color, morphology, and star formation rates of galaxies. But at which stages of cluster formation, in which epochs of the Universe, did galaxy clusters begin on average to have a substantial excess of early-type galaxies? Did early clusters simply form from massive precociously-quenched galaxies as a rule, or did they quench their galaxies later as they built up halo mass, or some mixture of both scenarios? With the SpARCS and GOGREEN surveys, we study galaxy clusters between redshifts 1 and 1.7 to understand better how they came to be dominated by early-type galaxies. Early results from SpARCS at z > 1.3 show that the conversion fraction (environmental quenching efficiency) in clusters of ordinary richness increases between z 1.6 and z 1.3, indicating these clusters are not born dominated by mass-quenched early types. Future results from GOGREEN should help constrain the onset of quenching in clusters.