Exploring the relation between turbulent velocity and density fluctuations in the stratified intracluster medium

M. Simonte, F. Vazza, F. Brighenti, M. Brüggen, T. W. Jones, M. Angelinelli

Research output: Contribution to journalArticlepeer-review

Abstract

Context. The dynamics of the intracluster medium (ICM) is affected by turbulence driven by several processes, such as mergers, accretion and feedback from active galactic nuclei. Aims. X-ray surface brightness fluctuations have been used to constrain turbulence in galaxy clusters. Here, we use simulations to further investigate the relation between gas density and turbulent velocity fluctuations, with a focus on the effect of the stratification of the ICM. Methods. In this work, we studied the turbulence driven by hierarchical accretion by analysing a sample of galaxy clusters simulated with the cosmological code ENZO. We used a fixed scale filtering approach to disentangle laminar from turbulent flows. Results. In dynamically perturbed galaxy clusters, we found a relation between the root mean square of density and velocity fluctuations, albeit with a different slope than previously reported. The Richardson number is a parameter that represents the ratio between turbulence and buoyancy, and we found that this variable has a strong dependence on the filtering scale. However, we could not detect any strong relation between the Richardson number and the logarithmic density fluctuations, in contrast to results by recent and more idealised simulations. In particular, we find a strong effect from radial accretion, which appears to be the main driver for the gas fluctuations. The ubiquitous radial bias in the dynamics of the ICM suggests that homogeneity and isotropy are not always valid assumptions, even if the turbulent spectra follow Kolmogorov's scaling. Finally, we find that the slope of the velocity and density spectra are independent of cluster-centric radii.

Original languageEnglish (US)
JournalAstronomy and Astrophysics
Volume658
DOIs
StatePublished - Feb 1 2022

Bibliographical note

Funding Information:
Acknowledgements. The authors thank Xun Shi for providing data for Sect. 2.3. The cosmological simulations described in this work were performed using the ENZO code (http://enzo-project.org), which is the product of a collaborative effort of scientists at many universities and national laboratories. F. V. acknowledges financial support from the European Union’s Horizon 2020 program under the ERC Starting Grant ‘MAGCOW’, no. 714196. Work by T.W.J. was supported by the US National Science Foundation grant AST1714205. MB acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany’s Excellence Strategy – EXC 2121 “Quantum Universe” – 390833306, Germany’s Excellence Strategy – EXC-2094 “Origins” – 390783311.

Funding Information:
The authors thank Xun Shi for providing data for Sect. 2.3. The cosmological simulations described in this work were performed using the ENZO code (http://enzo-project.org), which is the product of a collaborative effort of scientists at many universities and national laboratories. F. V. acknowledges financial support from the European Union's Horizon 2020 program under the ERC Starting Grant 'MAGCOW', no. 714196. Work by T.W.J. was supported by the US National Science Foundation grant AST1714205. MB acknowledges support by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation) under Germany's Excellence Strategy - EXC 2121 "Quantum Universe" - 390833306, Germany's Excellence Strategy - EXC-2094 "Origins" - 390783311.

Publisher Copyright:
© 2022 ESO.

Keywords

  • X-rays: galaxies: clusters
  • hydrodynamics
  • methods: numerical
  • turbulence

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