AGN jet-induced feedback in galaxies – II. Galaxy colours from a multicloud simulation |
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| Authors: | C Tortora V Antonuccio-Delogu S Kaviraj J Silk A D Romeo U Becciani |
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| Institution: | INAF –Osservatorio Astrofisico di Catania, Via S. Sofia 78, I-95123 Catania, Italy;Astrophysics, Department of Physics, University of Oxford, Keble Road, Oxford Ox1 3RH;Institute for Theoretical Astrophysics, University of Heidelberg, Albert-Ueberle-Str. 2, 69120 Heidelberg, Germany;Universidad Andres Bello, Departamento de Ciencias Fisicas, Av. Republica 252, Santiago, Chile |
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| Abstract: | We study the feedback from an active galactic nucleus (AGN) on stellar formation within its host galaxy, mainly using one high-resolution numerical simulation of the jet propagation within the interstellar medium (ISM) of an early-type galaxy (ETG). In particular, we show that in a realistic simulation where the jet propagates into a two-phase ISM, star formation (SF) can initially be slightly enhanced and then, on time-scales of few million years, rapidly quenched, as a consequence both of the high temperatures attained and of the reduction of cloud mass (mainly due to Kelvin–Helmholtz instabilities). We then introduce a model of (prevalently) negative AGN feedback, where an exponentially declining star formation is quenched, on a very short time-scale, at a time t AGN, due to AGN feedback. Using the Bruzual and Charlot population synthesis model and our SF history, we predict galaxy colours from this model and match them to a sample of nearby ETGs showing signs of recent episodes of SF, see Kaviraj et al. We find that the quantity t gal– t AGN , where t gal is the galaxy age, is an excellent indicator of the presence of feedback processes, and peaks significantly around t gal– t AGN≈ 0.85 Gyr for our sample, consistent with feedback from recent energy injection by AGNs in relatively bright ( M B??19) and massive nearby ETGs. Galaxies that have experienced this recent feedback show an enhancement of 3 mag in NUV ( GALEX ) ? g , with respect to the unperturbed, no-feedback evolution. Hence, they can be easily identified in large combined near UV-optical surveys. |
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| Keywords: | galaxies : elliptical and lenticular cD galaxies : evolution intergalactic medium galaxies: jets |
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