The combined effect of AGN and supernovae feedback in launching massive
  molecular outflows in high-redshift galaxies
  We have recently improved our model of active galactic nucleus (AGN) by
attaching the supermassive black hole (SMBH) to a massive nuclear star cluster
(NSC). Here we study the effects of this new model in massive, gas-rich
galaxies with several simulations of different feedback recipes with the
hydrodynamics code RAMSES. These simulations are compared to a reference
simulation without any feedback, in which the cooling halo gas is quickly
consumed in a burst of star formation. In the presence of strong supernovae
(SN) feedback, we observe the formation of a galactic fountain that regulates
star formation over a longer period, but without halting it. If only AGN
feedback is considered, as soon as the SMBH reaches a critical mass, strong
outflows of hot gas are launched and prevent the cooling halo gas from reaching
the disk, thus efficiently halting star formation, leading to the so-called
"quenching". If both feedback mechanisms act in tandem, we observe a non-linear
coupling, in the sense that the dense gas in the supernovae-powered galactic
fountain is propelled by the hot outflow powered by the AGN at much larger
radii than without AGN. We argue that these particular outflows are able to
unbind dense gas from the galactic halo, thanks to the combined effect of SN
and AGN feedback. We speculate that this mechanism occurs at the end of the
fast growing phase of SMBH, and is at the origin of the dense molecular
outflows observed in many massive high-redshift galaxies.
