Observable consequences of kinetic and thermal AGN feedback in elliptical galaxies and galaxy clusters

Edward C. D. Pope

doi:10.1111/j.1365-2966.2009.14714.x

paper

Observable consequences of kinetic and thermal AGN feedback in elliptical galaxies and galaxy clusters

arXiv:0903.0387 · doi:10.1111/j.1365-2966.2009.14714.x

Abstract

We have constructed an analytical model of 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 $\propto$ $σ^{8 - 10}$ , 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 $\propto L_{X} (< r_{cool}) / [g (r_{cool}) σ]$ , 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 $\sim 0.5$ Gyr, which is in reasonable agreement with recent observations showing that star formation and AGN activity are triggered below a universal cooling time threshold.

arXiv commentAccepted for publication in MNRAS, 11 pages, 2 figures and 2 tables

Observable consequences of kinetic and thermal AGN feedback in elliptical galaxies and galaxy clusters

Abstract

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