All galaxies host in their center a super-massive black hole, of mass between one million and a few billion solar masses. The mass of these black holes is proportional to the mass of the bulges of their galaxies, which suggests that star formation and feeding of black holes occur at the same rate and time: galaxies and their black holes grow in symbiosis.
When gas falls towards the center of the galaxy, the black hole swallows as much as possible, but the mass he can absorb is limited. The matter accretion on the black hole
releases a considerable amount of energy, in the form of radiation, and also in the form of kinetic energy. The galaxy nucleus becomes active, either a Seyfert, or a quasar. Winds and plasma jets emitted by the black hole entrain the surrounding interstellar gas. Molecular gas outflows have recently been detected around active nuclei, taking away so much mass that they can have a significant impact on the evolution of the host galaxy, regulating or even stopping gas supply for star formation.
The gluttonous black holes spitting their food, regulate star formation. These phenomena might be at the origin of the proportionality between masses of black holes and bulges.