Evolution of Cluster Ellipticals at 0.2 < [CLC][ITAL]z[/ITAL][/CLC] < 1.2 from [ITAL]Hubble Space Telescope[/ITAL] Imaging,

Two-dimensional surface photometry derived from Hubble Space Telescopeimaging is presented for a sample of 225 early-type galaxies (assumed to becluster members) in the fields of 9 clusters at redshifts $0.17 < z < 1.21$.The 94 luminous ellipticals ($M_{AB}(B)<-20$; selected by morphology alone withno reference to color) form tight sequences in the size-luminosity plane. Theposition of these sequences shifts, on average, with redshift so that an objectof a given size at z=0.55 is brighter by $\Delta M(B)=-0.57 \pm 0.13$ mag thanits counterpart (measured with the same techniques) in nearby clusters. Atz=0.9 the shift is $\Delta M(B)=-0.96 \pm 0.22$ mag. If the relation betweensize and luminosity is universal so that the local cluster galaxies representthe evolutionary endpoints of those at high redshift, and if thesize-luminosity relation is not modified by dynamical processes then thispopulation of galaxies has undergone significant luminosity evolution since z=1consistent with expectations based on models of passively evolving, old stellarpopulations.Comment: 7 pages, 3 figures, and 1 Tabl