Cluster Magnetic Fields

Carilli, C. L.; Taylor, G. B.

doi:10.1146/annurev.astro.40.060401.093852

Cited by 716 publications

(805 citation statements)

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“…Rotation measure observations through AGN radio lobes have shown cluster magnetic fields tangled on kiloparsec scales (Carilli & Taylor 2002). However, whether there is a turnover in the magnetic field power spectrum is difficult to determine from current data and is uncertain (e.g., Vogt & Enßlin 2003;Kuchar & Enßlin 2011).…”

Section: ( )mentioning

confidence: 99%

“…While it cannot by itself offset the radiative cooling in a stable manner (Stewart et al 1984;Bregman & David 1988;Soker 2003;Zakamska & Narayan 2003;Voigt & Fabian 2004;Pope et al 2006), it may provide part of the heating, reducing the burden on the AGN, and can aid in the isotropization of the AGN heating throughout the core. Second, the ICM is known to be magnetized with β∼100 (Carilli & Taylor 2002), where β is defined as the ratio between gas thermal pressure and magnetic pressure. Under conditions characterizing the ICM, conductive heat fluxes flow locally along magnetic field lines and are strongly suppressed across field lines (Spitzer 1962).…”

Section: Introductionmentioning

confidence: 99%

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Interplay Among Cooling, Agn Feedback, and Anisotropic Conduction in the Cool Cores of Galaxy Clusters

Yang

Reynolds

2016

ApJ

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Feedback from the active galactic nuclei (AGNs) is one of the most promising heating mechanisms to circumvent the cooling-flow problem in galaxy clusters. However, the role of thermal conduction remains unclear. Previous studies have shown that anisotropic thermal conduction in cluster cool cores (CCs) could drive the heat-flux-driven buoyancy instabilities (HBIs) that reorient the field lines in the azimuthal directions and isolate the cores from conductive heating from the outskirts. However, how the AGN interacts with the HBI is still unknown. To understand these interwined processes, we perform the first 3D magnetohydrodynamic simulations of isolated CC clusters that include anisotropic conduction, radiative cooling, and AGN feedback. We find the following: (1) For realistic magnetic field strengths in clusters, magnetic tension can suppress a significant portion of HBI-unstable modes, and thus the HBI is either completely inhibited or significantly impaired, depending on the unknown magnetic field coherence length. (2) Turbulence driven by AGN jets can effectively randomize magnetic field lines and sustain conductivity at ∼1/3 of the Spitzer value; however, the AGN-driven turbulence is not volumefilling. (3) Conductive heating within the cores could contribute to ∼10% of the radiative losses in Perseus-like clusters and up to ∼50% for clusters twice the mass of Perseus. (4) Thermal conduction has various impacts on the AGN activity and intracluster medium properties for the hottest clusters, which may be searched by future observations to constrain the level of conductivity in clusters. The distribution of cold gas and the implications are also discussed.

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Section: ( )mentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Interplay Among Cooling, Agn Feedback, and Anisotropic Conduction in the Cool Cores of Galaxy Clusters

Yang

Reynolds

2016

ApJ

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“…Recent studies have inferred magnetic field intensities between 0.1 and a few µG at the virial radius [54][55][56] 0.1 µG, while observations of radio relics support magnetic field strengths that can be even larger than 3 µG [57,58]. Equipartition models suggest a still larger magnetic field, with an intensity of approximately 10 µG around the virial radius [59].…”

Section: Magnetic Fieldsmentioning

confidence: 98%

Anisotropy of the extragalactic radio background from dark matter annihilation

Fang

Linden

2015

Phys. Rev. D

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Observations of the extragalactic radio background have uncovered a significant isotropic emission across multiple frequencies spanning from 22 MHz to 10 GHz. The intensity of this non-thermal emission component significantly exceeds the expected contribution from known astrophysical sources. Interestingly, models have indicated that the annihilation of dark matter particles may reproduce both the flux and spectrum of the excess. However, the lack of a measurable anisotropy in the residual emission remains challenging for both dark matter and standard astrophysical interpretations of the ARCADE-2 data. We calculate the expected synchrotron anisotropy from dark matter annihilation and show that these models can produce very small anisotropies, though this requires galaxy clusters to have large substructure contributions and strong magnetic fields. We show that this constraint can be significantly relaxed, however, in scenarios where electrons produced via dark matter annihilation can be efficiently reaccelerated by Alfvén waves in the intra-Cluster medium. Our analysis indicates that any source capable of explaining the intensity and isotropy of the extragalactic radio excess must have a spatial extension far larger than typical for baryons in galaxies, hinting at a novel physics interpretation.

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“…In this section we briefly report on the main observational results on cosmic magnetic fields and on physical models for their generation in the early universe and their evolution (see, e.g., Kronberg (1994), Grasso andRubinstein (2001), Carilli and Taylor (2002), Widrow (2002) for reviews).…”

Section: Magnetic Fields In Cosmologymentioning

confidence: 99%