Talk Title: Feedback from quasars in galaxy formation
Abstract: The main structural, photometrical and chemical properties of elliptical galaxies suggest that most of their stars formed in a quick starburst at high redshift, eventually interrupted by a strong galactic wind. Quasar activity is a plausible trigger for such a wind. However, the mechanism by which gas is accelerated and removed from a very bright galaxy is still unclear. I propose a scenario in which the joint action of photo-evaporation by the quasar and feedback from SNe trigger the wind. In a typical forming spheroid with multi-phase ISM, an equilibrium configuration is reached where most mass is in low-filling factor cold clouds, while shock waves from exploding type II SNe are pressure-confined in the adiabatic phase by a pervasive hot diffuse phase. Photo-evaporation by the quasar causes a quick and significant mass transfer from the cold clouds to the hot diffuse phase, making the latter much denser. SNRs then become radiative, working to collapse the hot phase into cold clouds to get back to the equilibrium configuration. We show that in this case SNRs percolate the volume, creating a giant galaxy-wide super-bubble. Some gas will be compressed to the centre, feeding the black hole and giving rise to nuclear star formation. In this situation radiation pressure from the quasar and new SNe will pump more energy into the super-bubble. Finally, the consequences of this process on the statistical properties of ellipticals and remnant black holes will be outlined.
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