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Using deep near-infrared spectroscopy Kriek et al. (2006) found that ~45% of massive galaxies at z~2.3 have evolved stellar populations and little or no ongoing star formation. Here we determine the sizes of these quiescent galaxies using deep, high-resolution images obtained with HST/NIC2 and laser guide star-assisted Keck/AO. Considering that their median stellar mass is 1.7x10^11 Solar masses the galaxies are remarkably small, with a median effective radius of 0.9 kpc. Galaxies of similar mass in the nearby Universe have sizes of ~5 kpc and average stellar densities which are two orders of magnitude lower than the z~2.3 galaxies. These results extend earlier work at z~1.5 and confirm previous studies at z>2 which lacked spectroscopic redshifts and imaging of sufficient resolution to resolve the galaxies. Our findings demonstrate that fully assembled early-type galaxies make up at most ~10% of the population of K-selected quiescent galaxies at z~2.3, effectively ruling out simple monolithic models for their formation. The galaxies must evolve significantly after z~2.3, through dry mergers or other processes, consistent with predictions from hierarchical models.
[Abridged] Using public data from the NMBS and CANDELS surveys, we study the population of massive galaxies at z>3 to identify the potential progenitors of z~2 compact, massive, quiescent (CMQ) galaxies, furthering our understanding of the evolution
[abridged] The mass-size relation of early-type galaxies (ETGs) has been largely studied in the last years to probe the mass assembly of the most massive objects in the Universe. In this paper, we focus on the mass-size relation of quiescent massive
We have used the Hubble Space Telescopes Advanced Camera for Surveys (Ford et al. 2003) to measure the cumulative mass density in morphologically-selected early-type galaxies over the redshift range 0.8 < z < 1.7. Our imaging data set covers four wel
ABRIDGED: We study the evolution since z~1 of the rest-frame B luminosity function of the early-type galaxies (ETGs) in ~0.7 deg^2 in the COSMOS field. In order to identify ALL progenitors of local ETGs we construct the sample of high-z galaxies usin
We examine the Fundamental Plane (FP) and mass-to-light ratio ($M/L$) scaling relations using the largest sample of massive quiescent galaxies at $1.5<z<2.5$ to date. The FP ($r_{e}, sigma_{e}, I_{e}$) is established using $19$ $UVJ$ quiescent galaxi