Observable consequences of kinetic and thermal AGN feedback in elliptical galaxies and galaxy clusters |
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Authors: | Edward C D Pope |
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Institution: | School of Physics &Astronomy, University of Victoria, Victoria, BC, V8P 1A1, Canada |
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Abstract: | We have constructed an analytical model of active galactic nuclei (AGN) feedback and studied its implications for elliptical galaxies and galaxy clusters. The results show that momentum injection above a critical value will eject material from low-mass elliptical galaxies, and leads to an X-ray luminosity, L X, that is ∝σ8?10 , depending on the AGN fuelling mechanism, where σ is the velocity dispersion of the hot gas. This result agrees well with both observations and semi-analytic models. In more massive ellipticals and clusters, AGN outflows quickly become buoyancy dominated. This necessarily means that heating by a central cluster AGN redistributes the intracluster medium (ICM) such that the mass of hot gas, within the cooling radius, should be ∝ L X(< r cool)/ g ( r cool)σ] , where g ( r cool) is the gravitational acceleration at the cooling radius. This prediction is confirmed using observations of seven clusters. The same mechanism also defines a critical ICM cooling time of ~0.5 Gyr , which is in reasonable agreement with recent observations showing that star formation and AGN activity are triggered below a universal cooling time threshold. |
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Keywords: | hydrodynamics galaxies: active galaxies: clusters: general cooling flows galaxies: elliptical and lenticular cD |
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