  In order to understand the physical mechanisms at work during the formation
of massive early-type galaxies, we performed six zoomed hydrodynamical
cosmological simulations of halos in the mass range 4.3 10^12 < M_vir < 8.0
10^13 M_sun at z=0, using the Adaptive Mesh Refinement code RAMSES. These
simulations explore the role of Active Galactic Nuclei (AGN), through jets
powered by the accretion onto supermassive black holes on the formation of
massive elliptical galaxies. In the absence of AGN feedback, large amounts of
stars accumulate in the central galaxies to form overly massive, blue, compact
and rotation-dominated galaxies. Powerful AGN jets transform the central
galaxies into red extended and dispersion-dominated galaxies. This
morphological transformation of disc galaxies into elliptical galaxies is
driven by the efficient quenching of the in situ star formation due to AGN
feedback, which transform these galaxies into systems built up by accretion.
For galaxies mainly formed by accretion, the proportion of stars deposited
farther away from the centre increases, and galaxies have larger sizes. The
accretion is also directly responsible for randomising the stellar orbits,
increasing the amount of dispersion over rotation of stars as a function of
time. Finally, we find that our galaxies simulated with AGN feedback better
match the observed scaling laws, such as the size-mass, velocity
dispersion-mass, fundamental plane relations, and slope of the total density
profiles at z~0, from dynamical and strong lensing constraints.
