Active galactic nucleus (AGN) outflows can remove large quantities of gas from their host galaxy spheroids, potentially shutting off star formation. On the other hand, they can compress this gas, potentially enhancing or triggering star formation, at least for short periods. We present a set of idealized simulations of the AGN outflows affecting turbulent gas spheres, and investigate the effect of the outflow and the AGN radiation field upon gas fragmentation. We show that the AGN outflows of sufficient luminosity shut off fragmentation while the nucleus is active, but gas compression results in a burst of fragmentation after the AGN switches off. Self-shielding of gas against the AGN radiation field allows some fragmentation to occur during outbursts, but too much shielding results in a lower overall fragmentation rate. For our idealized simulation setup, there is a critical AGN luminosity, which results in the highest fragmentation rate, with outflows being too efficient at removing gas when L > Lcrit and not efficient enough to compress the gas to high densities otherwise. These results, although preliminary, suggest that the interaction between AGN and star formation in their host galaxies is particularly complex and requires careful study to interpret observations correctly.KZ is funded by the Research Council Lithuania through the National Science Programme grant no. LAT-09/2016. MAB acknowledges support by the ERC starting grant 638707 ‘BHs and their host galaxies: co-evolution across cosmic time.’ Simulations were performed on resources at the High Performance Computing Center HPC Sauletekis in Vilnius University Faculty of Physics
