Early-type Galaxies in the Hubble Deep Field. The-r_e relation and the lack of large galaxies at high redshift

We present the results of the detailed surface photometry of a sample of early–type galaxies in the Hubble Deep Field. Effective radii, surface brightnesses and total V 606 magnitudes have been obtained, as well as U 300 , B 450 , I 814 , J , H and K colors, which are compared with the predictions of chemical-spectrophotometric models of population synthesis. Spectroscopic redshifts are available for 23 objects. For other 25 photometric redshifts are given. In the < µ e > – r e plane the early–type galaxies of the HDF, once the appropriate K + E corrections are applied, turn out to follow the ‘ rest frame ’ Kormendy relation. This evidence, linked to the dynamical information gathered by Steidel et al. (1996), indicates that these galaxies, even at z ≃ 2 − 3, lie in the Fundamental Plane, in a virial equilibrium condition. At the same redshifts a statistically significant lack of large galaxies (i.e. with log r kpce > 0 . 2) is observed.