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Title: | Shaping the X-ray spectrum of galaxy clusters with AGN feedback and turbulence | Authors: | GASPARI, MASSIMO | Issue Date: | 2015 | Journal: | MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY. LETTERS | Number: | 451 | Issue: | 1 | First Page: | L60 | Abstract: | The hot plasma filling galaxy clusters emits copious X-ray radiation. The classic unheated and unperturbed cooling flow model predicts dramatic cooling rates and an isobaric X-ray spectrum with constant differential luminosity distribution. The observed cores of clusters (and groups) show instead a strong deficit of soft X-ray emission: dLx/dT ∝ (T/Thot)^{α = 2 ± 1}. Using 3D hydrodynamic simulations, we show that such deficit arises from the tight self-regulation between thermal instability condensation and AGN outflow injection: condensing clouds boost the AGN outflows, which quench cooling as they thermalize through the core. The resultant average distribution slope is α ≃ 2, oscillating within the observed 1 < α < 3. In the absence of thermal instability, the X-ray spectrum remains isothermal (α ≳ 8), while unopposed cooling drives a too shallow slope, α < 1. AGN outflows deposit their energy inside-out, releasing more heat in the inner cooler phase; radially distributed heating alone induces a declining spectrum, 1 < α < 2. Turbulence further steepens the spectrum and increases the scatter: the turbulent Mach number in the hot phase is subsonic, while it becomes transonic in the cooler phase, making perturbations to depart from the isobaric mode. Such increase in dln P/dln T leads to α ≈ 3. Self-regulated AGN outflow feedback can address the soft X-ray problem through the interplay of heating and turbulence. | URI: | http://hdl.handle.net/20.500.12386/29291 | URL: | https://academic.oup.com/mnrasl/article/451/1/L60/955719 | ISSN: | 1745-3933 | DOI: | 10.1093/mnrasl/slv067 | Bibcode ADS: | 2015MNRAS.451L..60G | Fulltext: | open |
Appears in Collections: | 1.01 Articoli in rivista |
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