The faint end of the galaxy luminosity function in Abell 1689: a steep
  red faint end upturn at $z=0.18$
  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 $10'$ 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.
