Jet-induced star formation in gas-rich galaxies

Abstract

This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society. ?? 2012 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved. The version of record is available online at doi:10.1111/j.1365-2966.2012.21479.x.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 of quenching 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 M) 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 yr, 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 M for one duty cycle. We discuss the details of this jet-induced star formation (positive feedback) and its potential consequences for galaxy evolution and observable signatures

Observational evidence that positive and negative AGN feedback depends on galaxy mass and jet power

“…This excess corresponds to about a factor of two. A similar increase in SFR due to the onset of radio jets has been suggested also by simulations of massive, gas-rich, high-redshift galaxies (Silk & Nusser 2010;Gaibler et al 2012).…”

“…van Breugel et al 2004;Gaibler et al 2012;Wagner et al 2012;Ishibashi & Fabian 2012). Simulations have shown that, although powerful jets' interaction with the ISM might be volume limited, the resulting pressure can impact the galactic disk also at larger radii and eventually all of the galaxy (see Gaibler et al 2012). Thermal or kinetic AGN feedback is often thought to heat and expel most residual gas from the galaxy (e.g.…”

Herschel-ATLAS: the connection between star formation and AGN activity in radio-loud and radio-quiet active galaxies

“…Bower et al 2006;Werner et al 2013;Chen et al 2013b). However, a positive radio mode feedback has also been suggested (Silk & Nusser 2010;Kalfountzou et al 2012Kalfountzou et al , 2014Gaibler et al 2012). In this scenario, the radio jets drive shocks in the interstellar medium which enhance the star formation, something that has been observed for decades now (e.g.…”

Enhancing and inhibiting star formation: high-resolution simulation studies of the impact of cold accretion, mergers and feedback on individual massive galaxies

“…Right: Image of jet interacting with cold gas disc and a hot ambient medium. See Gaibler et al (2012) for details of the jet modeling. resolution) with orbital parameters that can be considered 'average' for a LCDM cosmology.…”

“…Jets could potentially keep the hot halo hot, preventing 16 L. C. Powell et al it from being a fuel supply. We are currently testing simulations which combine idealised merger simulations including hot gas haloes with the jet module presented in Gaibler et al (2012) (see Fig. 2,, in order to address this issue.…”