Active galactic nuclei and massive galaxy cores

¹ Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH, UK e-mail: [sp;silk]@astro.ox.ac.uk
² Institut d'Astrophysique de Paris, 98 bis Bd Arago, 75014 Paris; Unité mixte de recherche 7095 CNRS, Université Pierre et Marie Curie, France
³ Jodrell Bank Centre for Astrophysics, Alan Turing Building, School of Physics and Astronomy, The University of Manchester, Manchester M13 9PL, UK e-mail: Scott.Kay@manchester.ac.uk

Received: 27 May 2007
Accepted: 30 November 2007

Abstract

Context.Central active galactic nuclei (AGN) are supposed to play a key role in the evolution of their host galaxies. In particular, the dynamical and physical properties of the gas core must be affected by the injected energy.

Aims.Our aim is to study the effects of an AGN on the dark matter profile and on the central stellar light distribution in massive early type galaxies.

Methods.By performing self-consistent N-body simulations, we assume in our analysis that periodic bipolar outbursts from a central AGN can induce harmonic oscillatory motions on both sides of the gas core.

Results.Using realistic AGN properties, we find that the motions of the gas core, driven by such feedback processes, can flatten the dark matter and/or stellar profiles after 4-5 Gyr. These results are consistent with recent observational studies that suggest that most giant elliptical galaxies have cores or are “missing light” in their inner part. Since stars behave as a “collisionless” fluid similar to dark matter, the density profile both of stars and dark matter should be affected in a similar way, leading to an effective reduction in the central brightness.