Disk dynamics at high redshift: the growth of bulges and black holes and the properties of star formation and feedback
Galaxies at high redshift are very gas rich and subject to violent disk instabilities, with in particular giant clumps of gas and star formation that are observed with the HST and VLT. The clumps can migrate and grow a stellar spheroid, they also drive an intense inflow toward the stellar bulge and central supermassive black hole. Both stellar and AGN feedback may leave the gas clumps unaffected even if they trigger intense gas outflows from the galaxy. Models with strong feedback however predict that the clumps are short-lived and the disk rapidly stabilized. However, examining the detailed properties of star formation at high resolution, including in nearby galaxies, leads to the conclusion that the low efficiency of star formation is mostly ensured by turbulent pressure rather requiring strong feedback. Models with relatively weak feedback and regulated star formation can provide better explanations for observed galaxy morphologies. Nevertheless, the regulation of galaxy mass growth at early epochs remains largely mysterious and I will discuss recent ideas on this topic.