A<i>SUZAKU</i>SEARCH FOR NONTHERMAL EMISSION AT HARD X-RAY ENERGIES IN THE COMA CLUSTER

Wik, Daniel R.; Sarazin, Craig L.; Finoguenov, A.; Matsushita, Kyoko; Nakazawa, K.; Clarke, T. E.

doi:10.1088/0004-637x/696/2/1700

Cited by 66 publications

(144 citation statements)

References 63 publications

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“…These efforts have thus derived lower limits for the magnetic field strength, over areas smaller than the radio halo. The lower limit reported by Wik et al (2009) is e.g. B > 0.2 μG, that is compatible with our results.…”

Section: Comparison With Other Estimatessupporting

confidence: 93%

“…The values computed here indicate however that they can be reconciled. Recently, new hard X-ray observations of the Coma cluster have been performed with the new generation of satellites (see the work by Wik et al 2009, using XMM and Suzaku data, Lutovinov et al 2008, using ROSAT, RXTE and INTEGRAL data, Ajello et al 2009, using XMM-Newton, Swift/XRT, Chandra and BAT data). These observations failed to find statistically significant evidence for non-thermal emission in the hard X-ray spectrum of the ICM, which is better described by a single or multi-temperature model.…”

Section: Comparison With Other Estimatesmentioning

confidence: 99%

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The Coma cluster magnetic field from Faraday rotation measures

Bonafede

Feretti

Murgia

et al. 2010

A&A

430

667

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Aims. The aim of the present work is to constrain the Coma cluster magnetic field strength, its radial profile and power spectrum by comparing Faraday rotation measure (RM) images with numerical simulations of the magnetic field. Methods. We have analyzed polarization data for seven radio sources in the Coma cluster field observed with the Very Large Array at 3.6, 6 and 20 cm, and derived Faraday rotation measures with kiloparsec scale resolution. Random three dimensional magnetic field models have been simulated for various values of the central intensity B 0 and radial power-law slope η, where η indicates how the field scales with respect to the gas density profile. Results. We derive the central magnetic field strength, and radial profile values that best reproduce the RM observations. We find that the magnetic field power spectrum is well represented by a Kolmogorov power spectrum with minimum scale ∼2 kpc and maximum scale ∼34 kpc. The central magnetic field strength and radial slope are constrained to be in the range (B 0 = 3.9 μG; η = 0.4) and (B 0 = 5.4 μG; η = 0.7) within 1σ. The best agreement between observations and simulations is achieved for B 0 = 4.7 μG; η = 0.5. Values of B 0 > 7 μG and <3 μG as well as η < 0.2 and η > 1.0 are incompatible with RM data at 99% confidence level.

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Section: Comparison With Other Estimatessupporting

confidence: 93%

Section: Comparison With Other Estimatesmentioning

confidence: 99%

The Coma cluster magnetic field from Faraday rotation measures

Bonafede

Feretti

Murgia

et al. 2010

A&A

430

667

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“…The observations and processed XMM-Newton data used herein are identical to that presented in Wik et al (2009), where a more detailed description can be found. The XMM-Newton EPIC-pn mosaic of Coma consists of 14 individual pointings, the first set (11 pointings) of which were discussed in Briel et al (2001).…”

Section: Xmm-newton Epic-pn Mosaic Observationsmentioning

confidence: 99%

THE LACK OF DIFFUSE, NON-THERMAL HARD X-RAY EMISSION IN THE COMA CLUSTER: THESWIFTBURST ALERT TELESCOPE'S EYE VIEW

Wik¹,

Sarazin²,

Finoguenov³

et al. 2011

ApJ

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The Coma Cluster of galaxies hosts the brightest radio halo known and has therefore been the target of numerous searches for associated inverse Compton (IC) emission, particularly at hard X-ray energies where the IC signal must eventually dominate over thermal emission. The most recent search with the Suzaku Hard X-ray Detector failed to confirm previous IC detections with RXTE and BeppoSAX, instead setting an upper limit 2.5 times below their non-thermal flux. However, this discrepancy can be resolved if the IC emission is very extended, beyond the scale of the cluster radio halo. Using reconstructed sky images from the 58-month Swift Burst Alert Telescope (BAT) all-sky survey, the feasibility of such a solution is investigated. Building on Renaud et al., we test and implement a method for extracting the fluxes of extended sources, assuming specified spatial distributions. BAT spectra are jointly fit with an XMM-Newton EPIC-pn spectrum derived from mosaic observations. We find no evidence for large-scale IC emission at the level expected from the previously detected non-thermal fluxes. For all non-thermal spatial distributions considered, which span the gamut of physically reasonable IC models, we determine upper limits for which the largest (most conservative) limit is 4.2 × 10 −12 erg s −1 cm −2 (20-80 keV), which corresponds to a lower limit on the magnetic field B > 0.2 μ G. A nominal flux upper limit of <2.7 × 10 −12 erg s −1 cm −2 , with corresponding B > 0.25 μ G, is derived for the most probable IC distribution given the size of the radio halo and likely magnetic field radial profile.

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“…Fusco-Femiano 2004;Wik et al 2009;Ajello et al 2009;Murgia et al 2010a). Both of these methods require however several assumptions on the emitting particle distribution and energetic spectrum.…”

Section: Introductionmentioning

confidence: 99%

Fractional polarization as a probe of magnetic fields in the intra-cluster medium

Bonafede

Govoni

Feretti

et al. 2011

A&A

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Context. It is now established that magnetic fields are present in the intra-cluster medium (ICM) of galaxy clusters, as revealed by observations of radio halos and radio relics and from the study of the Faraday rotation measures of sources located either behind or within clusters. Deep radio polarization observations of clusters have been performed in the last years, and the properties of the ICM magnetic field have been constrained in a small number of well-studied objects. Aims. The aim of this work is to investigate the average properties of the ICM magnetic fields, and to search for possible correlations with the ICM thermal properties and cluster radio emission. Methods. We have selected a sample of 39 massive galaxy clusters from the HIghest X-ray FLUx Galaxy Cluster Sample, and used Northern VLA Sky Survey data to analyze the fractional polarization of radio sources out to 10 core radii from the cluster centers. We have investigated how different magnetic field strengths affect the observed polarized emission of sources lying at different projected distances from the cluster center. In addition, statistical tests are performed to investigate the fractional polarization trends in clusters with different thermal and non-thermal properties. Results. We find a trend of the fractional polarization with the cluster impact parameter, with fractional polarization increasing at the cluster periphery and decreasing toward the cluster center. Such trend can be reproduced by a magnetic field model with central value of few μG. The logrank statistical test indicates that there are no differences in the depolarization trend observed in cluster with and without radio halo, while the same test indicates significant differences when the depolarization trend of sources in clusters with and without cool core are compared. The comparison between clusters with high and low temperatures does not yields significant differences. Although the role of the gas density should be better accounted for, these results give important indications for models that require a role of the ICM magnetic field to explain the presence of cool core and radio halos in galaxy clusters.

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ASUZAKUSEARCH FOR NONTHERMAL EMISSION AT HARD X-RAY ENERGIES IN THE COMA CLUSTER

Cited by 66 publications

References 63 publications

The Coma cluster magnetic field from Faraday rotation measures

The Coma cluster magnetic field from Faraday rotation measures

THE LACK OF DIFFUSE, NON-THERMAL HARD X-RAY EMISSION IN THE COMA CLUSTER: THESWIFTBURST ALERT TELESCOPE'S EYE VIEW

Fractional polarization as a probe of magnetic fields in the intra-cluster medium

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