Gas replenishing mechanism(s) and the role of the large-scale environment
Thaisa Storchi Bergmann (Invited)
The observed coevolution of supermassive black holes (SMBH) and galaxies is partly due to the fact that both feed on gas accreting into the central region of galaxies. Indeed, recent stellar population studies of the inner kpc of Active Galactic Nuclei (AGN) hosts – where the nuclear SMBH is growing, indicate an excess of young to intermediate age (~100 Myr) stars. This suggests that the AGN triggering occurs following a gas inflow that forms stars in its way towards the galaxy nucleus. I will discuss what we know about the large scale environment of AGN and signatures of their triggering: in the most luminous sources, major mergers are frequent, while in low luminosity AGNs subtle asymmetries on the host galaxy images also suggest external gas capture – e.g. via chaotic cold accretion, a minor merger or secular processes in the late-type host galaxies. While bars do not appear to directly feed AGNs, AGN flickering leads to the dissociation between small and large scales, hence affecting the interpretation of cause and effect. At ~100 pc scales, recent observations have revealed compact disks and inflows along nuclear gaseous spirals and bars, both in ionized and molecular gas, while chaotic cold accretion continues to feed luminous early-type galaxies at these scales.