Florian Dedieu

Supermassive black holes (with masses ranging from one million to one billion solar masses) seem to reside at the center of all massive galaxies. For the last decades, the processes involved in their formation and evolution have been intensively studied, both observationally and numerically, in order to understand how they obtain their masses and evolve with their host galaxies. Accretion of gas by those black holes translate into the strong luminosity of galactic nuclei and, sometimes, into galactic jets. However, it is complex to understand how the gas from galactic disks loses its angular momentum and falls very near from the black holes. On kpc-scales, mechanisms such as the torques exerted by a stellar bar on gas allow this exchange of angular momentum. This phenomenon could be made possible up to some parsecs from the black hole through the influence of a nuclear bar. First observations at very high angular resolution of the molecular gas in the central regions of galaxies with such nuclear bars show nuclear spirals of gas on scales ranging from 10 to 100 pc. The nature of their geometry (’trailing’) is such as the torques exerted on the gas is negative, allowing it to fall towards the black hole. Nevertheless, the formation of such structures has been very little studied numerically. This is what we propose to do in this thesis, through numerical simulations of gas accretion on these scales, a quantification of the angular momentum lost by gas and of the quantity of gas that can eventually feed the central black hole. These simulations will be of an exploratory and innovative nature and will participate in understanding how are supermassive black holes supplied with gas and, therefore, on the close connection between the evolution of the properties of supermassive black holes and those of their host galaxies.