Observations of magnetic fields in regular and irregular clusters

Govoni, F.

doi:10.1002/asna.200610583

Cited by 16 publications

(9 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We also stress that present data do not show a clear connection between the magnetic field properties and cluster dynamics (e.g. Clarke, Kronberg & Böhringer 2001; Govoni 2006) that leaves the process of magnetic field amplification still poorly constrained.…”

Section: Resultscontrasting

confidence: 57%

Acceleration of primary and secondary particles in galaxy clusters by compressible MHD turbulence: from radio haloes to gamma-rays

Brunetti¹,

Lazarían²

2010

Monthly Notices of the Royal Astronomical Society

180

177

View full text Add to dashboard Cite

Radio observations discovered large‐scale non‐thermal sources in the central Mpc regions of dynamically disturbed galaxy clusters (radio haloes). The morphological and spectral properties of these sources suggest that the emitting electrons are accelerated by spatially distributed and gentle mechanisms, providing some indirect evidence for turbulent acceleration in the intergalactic medium (IGM). Only deep upper limits to the energy associated with relativistic protons in the IGM have been recently obtained through gamma and radio observations. Yet these protons should be (theoretically) the main non‐thermal particle component in the IGM implying the unavoidable production, at some level, of secondary particles that may have a deep impact on the gamma‐ray and radio properties of galaxy clusters. Following Brunetti & Lazarian, in this paper we consider the advances in the theory of magnetohydrodynamics (MHD) turbulence to develop a comprehensive picture of turbulence in the IGM and extend our previous calculations of particle acceleration by compressible MHD turbulence by considering self‐consistently the re‐acceleration of both primary and secondary particles. Under these conditions we expect that radio to gamma‐ray emission is generated from galaxy clusters with a complex spectrum that depends on the dynamics of the thermal gas and dark matter. The non‐thermal emission results in very good agreement with radio observations and with present constraints from hard X‐ray and gamma‐ray observations. In our model giant radio haloes are generated in merging (turbulent) clusters only. However, in case secondaries dominate the electron component in the IGM, we expect that the level of the Mpc‐scale synchrotron emission in more relaxed clusters is already close to that of the radio upper limits derived by present observations of clusters without radio haloes. Important constraints on cluster physics from future observations with present and future telescopes are also discussed.

show abstract

Section: Resultscontrasting

confidence: 57%

Acceleration of primary and secondary particles in galaxy clusters by compressible MHD turbulence: from radio haloes to gamma-rays

Brunetti¹,

Lazarían²

2010

Monthly Notices of the Royal Astronomical Society

180

177

View full text Add to dashboard Cite

show abstract

“…Magnetic fields can modify the transport coefficients significantly because the ratio of the Coulomb mean free path to the Larmor radius of a thermal proton is ≃ 10 8 B(kT ) 3/2 n −1 e , where the magnetic field, B, is in µG, the temperature, kT , is in keV, and n e is the electron density in cm −3 . The same ratio for electrons is a factor of m p /m e larger, so that electrons and ions are both tied rigidly to magnetic field lines for typical values of the intracluster magnetic field (e.g., Govoni 2006). One might then expect thermal conduction and viscous forces to be controlled entirely by the structure of the magnetic field (e.g., Tribble 1989).…”

Section: Transport Coefficientsmentioning

confidence: 99%

Heating Hot Atmospheres with Active Galactic Nuclei

McNamara

Nulsen

2007

Annu. Rev. Astron. Astrophys.

1,313

1,224

View full text Add to dashboard Cite

High resolution X-ray spectroscopy of the hot gas in galaxy clusters has shown that the gas is not cooling to low temperatures at the predicted rates of hundreds to thousands of solar masses per year. X-ray images have revealed giant cavities and shock fronts in the hot gas that provide a direct and relatively reliable means of measuring the energy injected into hot atmospheres by active galactic nuclei (AGN). Average radio jet powers are near those required to offset radiative losses and to suppress cooling in isolated giant elliptical galaxies, and in larger systems up to the richest galaxy clusters. This coincidence suggests that heating and cooling are coupled by feedback, which suppresses star formation and the growth of luminous galaxies. How jet energy is converted to heat and the degree to which other heating mechanisms are contributing, eg. thermal conduction, are not well understood. Outburst energies require substantial late growth of supermassive black holes. Unless all of the approximately 10E62 erg required to suppress star formation is deposited in the cooling regions of clusters, AGN outbursts must alter large-scale properties of the intracluster medium.Comment: 60 pages, 12 figures, to appear in 1997 Annual Reviews of Astronomy and Astrophysics. This version supersedes the April 2007 version in Reviews in Advance (references and minor corrections were added), and is similar to the one scheduled to appear in Volume 45 of ARA

show abstract

“…Therefore, even if the central magnetic field does increase with cluster mass, a constant mean magnetic field could still be inferred, if the shape of the radial field profile decreases properly. Furthermore, although indications for a radial dependence of the magnetic field can be inferred from clusters where rotation measures of several radio galaxies are available (Dolag et al 2001b; Murgia et al 2004; Govoni 2006), there still exits a large degeneracy between the parameters describing the magnetic field in clusters (Bonafede et al 2008; Guidetti et al 2008). Hence, it is quite important to compare the observed scalings with the predictions from simulations.…”

Section: Cluster‐based Analysismentioning

confidence: 99%

Cluster magnetic fields from galactic outflows

Donnert

Dolag

Lesch

et al. 2009

Monthly Notices of the Royal Astronomical Society

168

207

View full text Add to dashboard Cite

We performed cosmological, magnetohydrodynamical simulations to follow the evolution of magnetic fields in galaxy clusters, exploring the possibility that the origin of the magnetic seed fields is galactic outflows during the starburst phase of galactic evolution. To do this, we coupled a semi‐analytical model for magnetized galactic winds as suggested by Bertone, Vogt & Enßlin to our cosmological simulation. We find that the strength and structure of magnetic fields observed in galaxy clusters are well reproduced for a wide range of model parameters for the magnetized, galactic winds and do only weakly depend on the exact magnetic structure within the assumed galactic outflows. Although the evolution of a primordial magnetic seed field shows no significant differences to that of galaxy cluster fields from previous studies, we find that the magnetic field pollution in the diffuse medium within filaments is below the level predicted by scenarios with pure primordial magnetic seed field. We therefore conclude that magnetized galactic outflows and their subsequent evolution within the intracluster medium can fully account for the observed magnetic fields in galaxy clusters. Our findings also suggest that measuring cosmological magnetic fields in low‐density environments such as filaments is much more useful than observing cluster magnetic fields to infer their possible origin.

show abstract

Observations of magnetic fields in regular and irregular clusters

Cited by 16 publications

References 37 publications

Acceleration of primary and secondary particles in galaxy clusters by compressible MHD turbulence: from radio haloes to gamma-rays

Acceleration of primary and secondary particles in galaxy clusters by compressible MHD turbulence: from radio haloes to gamma-rays

Heating Hot Atmospheres with Active Galactic Nuclei

Cluster magnetic fields from galactic outflows

Contact Info

Product

Resources

About