Disk and spheroid formation in the cosmological context
Star forming galaxies above redshift one have increasingly clumpy morphology, 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. Clump form in turbulent disks and migrate
inwards. They redistribute the disk material in an exponential profile. When massive enough, clumps can reach the center of the system and coalesce to form or grow a bulge, together with its supermassive nuclear black hole. Bulge properties in our models closely resemble the classical bulges observed in early-type spirals. The thick disks of today's spiral galaxies are likely leftovers that attest of this past evolutionary processes. 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. Resolved galaxy properties at all redshifts actually constrain how their mass was assembled. Whether or not the standard L-CDM paradigm can account for galaxy properties is still a largely unknown, and I will show recent progress in modelling the properties of galaxies at high resolution in the full cosmological context.