  We report on a complete sample of 7 luminous early-type galaxies in the
Hubble Ultra Deep Field (UDF) with spectroscopic redshifts between 1.39 and
2.47 and to K<23 AB. Using the BzK selection criterion we have pre-selected a
set of objects over the UDF which fulfill the photometric conditions for being
passively evolving galaxies at z>1.4. Low-resolution spectra of these objects
have been extracted from the HST+ACS grism data taken over the UDF by the
GRAPES project. Redshift for the 7 galaxies have been identified based on the
UV feature at rest frame 2640<lambda<2850 AA. This feature is mainly due to a
combination of FeII, MgI and MgII absorptions which are characteristic of
stellar populations dominated by stars older than about 0.5 Gyr. The redshift
identification and the passively evolving nature of these galaxies is further
supported by the photometric redshifts and by the overall spectral energy
distribution (SED), with the ultradeep HST+ACS/NICMOS imaging revealing compact
morphologies typical of elliptical/early-type galaxies. From the SED we derive
stellar masses of 10^{11}Msun or larger and ages of about 1 Gyr. Their space
density at < z >=1.7 appears to be roughly a factor of 2--3 smaller than that
of their local counterparts, further supporting the notion that such massive
and old galaxies are already ubiquitous at early cosmic times. Much smaller
effective radii are derived for some of the objects compared to local massive
ellipticals, which may be due to morphological K corrections, evolution, or the
presence of a central point-like source. Nuclear activity is indeed present in
a subset of the galaxies, as revealed by them being hard X-ray sources, hinting
to AGN activity having played a role in discontinuing star formation.
