Disk and spheroid formation in the cosmological context
F. Bournaud

Abstract :
Star forming galaxies above redshift one have increasingly clumpy morphologies, often taking the appearance of chain galaxies and clump clusters. A large fraction of their mass is gathered into a few kpc-sized blobs. While the morphology of such systems could resemble groups of proto-galaxies in a hierarchical merging process, I will show evidence that these are actually massive, gas-rich disks, that fragmented by gravitational instabilities. Numerical models are used to study the evolution of such systems, and suggest that today's spiral galaxies were shaped by the internal, clump-driven evolution of primordial disks. Clumps redistribute the disk material in an exponential profile. When massive enough, clumps can reach the center of the system and coalesce to form a bulge. The thick disks of today's spiral galaxies are likely leftovers that attest of this past evolutionary processes. The ISM of such z~2 clumpy galaxies, which are the progenitors of today's Milky Way-like spirals, is observed to be starbursting over the whole disk with high pressures and efficiencies.
  Major and minor mergers do not appear to be the main drivers of galactic mass assembly and star formation history. The clumpiness of high-redshift disk implies that they are strongly self-gravitating, which constrain the role of mergers and smooth gas infall in the mass assembly of galaxies. Whether or not the standard L-CDM paradigm can account for galaxy properties at high and low redshift is still largely unknown, and I will show recent progress in modelling the properties of galaxies at high resolution in the cosmological context.