We present a deep and wide I luminosity function for galaxies in Abell 1689 ( z = 0.183 ) from a mosaic of HST WFPC2 images covering 10 ^ { \prime } on the side .
The main result of this work is the detection of a steep upturn in the dwarf galaxy LF , with \alpha \sim - 2 .
The dwarf to giant ratio appears to increase outwards , but this is because giant galaxies are missing in the cluster outskirts , indicating luminosity segregation .
The red sequence LF has the same parameters , within errors , as the total LF , showing that the faint end upturn consists of red quiescent galaxies .
We speculate that the upturn is connected to the ‘ filling-in ’ of the red sequence at z < 0.4 and may represent the latest installment of ‘ downsizing ’ as the least massive galaxies are being quenched at the present epoch .