Conférence de Sirio Belli, Max Planck Institute for Extraterrestrial Physics
Understanding how massive galaxies formed and assembled their stars is one of the major challenges for extragalactic astronomy. Using the new generation of sensitive near-infrared spectrographs at Keck and VLT, we have investigated the physical properties of massive quiescent galaxies at high redshift, including their stellar kinematics, star formation histories, and gas properties. I will show how these observations contribute to an emerging picture in which the star formation activity in massive galaxies is quenched at z~2-3 leaving compact, rapidly rotating quiescent objects. By accreting smaller quiescent systems, massive galaxies then grow in size and lose their angular momentum, turning into the giant ellipticals that we observe today. The physical mechanism that quenches their star formation in the first place is, however, still a mystery.