Volker Gaibler @ ITA

New paper on jet feedback accepted for MNRAS, available on astro-ph.

Feedback from active galactic nuclei (AGN) has become a major component in simulations of galaxy evolution, in particular for massive galaxies. AGN jets have been shown to provide a large amount of energy and are capable to quench cooling flows. Their impact on the host galaxy, however, is still not understood. Subgrid models of AGN activity in a galaxy evolution context so far have been mostly focused on the quenching of star formation. To shed more light on the actual physics of the "radio mode" part of AGN activity, we have performed simulations of the interaction of a powerful AGN jet with the massive gaseous disc (10¹¹ solar masses) of a high-redshift galaxy. We spatially resolve both the jet and the clumpy, multi-phase interstellar medium (ISM) and include an explicit star formation model in the simulation. Following the system over more than 10⁷ years, we find that the jet activity excavates the central region, but overall causes a significant change to the shape of the density probability distribution function and hence the star formation rate due to the formation of a blast wave with strong compression and cooling in the ISM. This results in a ring- or disc-shaped population of young stars. At later times, the increase in star formation rate also occurs in the disc regions further out since the jet cocoon pressurizes the ISM. The total mass of the additionally formed stars may be up to 10¹⁰ solar masses for one duty cycle. We discuss the details of this jet-induced star formation and its potential consequences for galaxy evolution and observable signatures.

Supplementary movies:

The evolution of star formation during the jet activity is shown in the following movies for the four simulations. It is shown as RGB composite, both face-on and edge-on. The jet is only switched on at t = 10 Myr; the evolution until then shows the quiescent (but still highly star-forming) disk.
Newly formed stars (formed within the last 1 Myr) are shown in blue, all other are shown either in red (stars formed within the first 10 Myr, where the jet was not yet active) or green (stars formed after 10$ Myr, when the jet was active).

For more movies and details on the hydrodynamics, see our previously published simulations "Asymmetries in Extragalactic Double Radio Sources: Clues from 3D Simulations of Jet - Disc Interaction".

Low star formation threshold (n = 0.1 / cm³), face-on view

Low star formation threshold (n = 0.1 / cm³), edge-on view

High star formation threshold (n = 5 / cm³), face-on view

High star formation threshold (n = 5 / cm³), edge-on view