AGN–starburst evolutionary connection: a physical interpretation based on radiative feedback

Abstract

Observations point towards a close connection between nuclear starbursts, active galactic nuclei (AGN), and outflow phenomena. An evolutionary sequence, starting from a dust-obscured ultra-luminous infrared galaxy and eventually leading to an unobscured optical quasar, has been proposed and discussed in the literature. AGN feedback is usually invoked to expel the obscuring gas and dust in a blow-out event, but the underlying physical mechanism remains unclear. We consider AGN feedback driven by radiation pressure on dust, which directly acts on the obscuring dusty gas. We obtain that radiative feedback can potentially disrupt dense gas in the infrared-optically thick regime, and that an increase in the dust-to-gas fraction leads to an increase in the effective Eddington ratio. Thus the more dusty gas is preferentially expelled by radiative feedback, and the central AGN is prone to efficiently remove its own obscuring dust cocoon. Large amounts of dust imply heavy obscuration but also powerful feedback, suggesting a causal link between dust obscuration and blow-out. In this picture, AGN feedback and starburst phenomena are intrinsically coupled through the production of dust in supernova explosions, leading to a natural interpretation of the observed evolutionary path.

On the origin of the dramatic spectral variability of WPVS 007

“…The derived R l values are 3 × 10 −3 pc and 3 × 10 −4 pc, respectively, which are all much smaller than the torus sublimation radius, thereby conflicting with our initial assumption that the outflows are launched in the torus. In addition, the fully absorbed scenario is also inconsistent with observations (Leighly et al 2009); and more sophisticated calculations of radiation pressure implementing on dusty gas from the torus also indicated that the typical maximum outflow velocity is a few thousand km s −1 and hardly reaches v > 10000 km s −1 , even if an enhanced dust to gas ratio is adopted for luminous dusty quasars (e.g., Ishibashi & Fabian 2016;Ishibashi et al 2017). Therefore, we argue that the outflows in WPVS 007 may most probable to be launched in the region closer to the black hole, and the torus origin maybe less likely.…”

The energetics of AGN radiation pressure-driven outflows

“…Banerji et al 2015). In a broader context, we have proposed how such radiative feedback, which directly acts on the obscuring dusty gas, may provide a natural physical interpretation for the observed co-evolutionary sequence (Ishibashi & Fabian 2016). Therefore AGN radiative feedback naturally fits in the global picture of 'black hole-host galaxy coevolution' scenarios.…”

Radiative AGN feedback on a moving mesh: the impact of the galactic disc and dust physics on outflow properties

“…To demonstrate that the numerical setup is performing as expected we require an analytic solution to compare with. As an AGN feedback channel, radiation pressure on dust has been well studied via analytical models (Murray et al 2005;Ishibashi & Fabian 2015;Thompson et al 2015;Ishibashi & Fabian 2016;Ishibashi et al 2018). We follow the analytic model presented in Ishibashi & Fabian (2015) and Thompson et al (2015), also see Costa et al (2018a).…”