Hard X-Ray Radiation in the Coma Cluster Spectrum

Fusco-Femiano, R.; Fiume, D. Dal; Feretti, L.; Giovannini, G.; Grandi, P.; Matt, Giorgio; Molendi, S.; Santangelo, A.

doi:10.1086/311902

Cited by 254 publications

(337 citation statements)

References 33 publications

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“…There is some observational evidence that modest magnetic fields are present throughout the ICM. The current measurements of intracluster magnetic fields are based on the Faraday rotation measure (RM) in radio sources seen through clusters (e.g., Kim et al 1991;Clarke et al 2001;Feretti et al 1999;Taylor et al 2001); direct evidence also comes from measurements of extended regions of radio synchrotron emission in clusters (see, e.g., Giovannini & Feretti 2000;Fusco-Femiano et al 1999;Owen et al 1999;Feretti 1999). Both the excess RM values and the radio halo data suggest modest magnetic fields, at a few microgauss levels, throughout the cluster.…”

Section: Introductionmentioning

confidence: 99%

Radiative Cooling and Heating and Thermal Conduction in M87

Ghizzardi

Molendi

Pizzolato

et al. 2004

ApJ

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The crisis of the standard cooling flow model brought about by Chandra and XMM-Newton observations of galaxy clusters has led to the development of several models that explore different heating processes in order to assess whether they can quench the cooling flow. Among the most appealing mechanisms are thermal conduction and heating through buoyant gas deposited in the intracluster medium (ICM) by active galactic nuclei (AGNs). We combine Virgo/M87 observations of three satellites (Chandra, XMM-Newton, and BeppoSAX ) to inspect the dynamics of the ICM in the center of the cluster. Using the spectral deprojection technique, we derive the physical quantities describing the ICM and determine the extra heating needed to balance the cooling flow, assuming that thermal conduction operates at a fixed fraction of the Spitzer value. We assume that the extra heating is due to buoyant gas, and we fit the data using the model developed by Ruszkowski and Begelman. We derive a scale radius for the model of $5 kpc, which is comparable with the M87 AGN jet extension, and a required luminosity of the AGN of a few ; 10 42 ergs s À1 , which is comparable to the observed AGN luminosity. We discuss a scenario in which the buoyant bubbles are filled with relativistic particles and magnetic field, which are responsible for the radio emission in M87. The AGN is supposed to be intermittent and to inject populations of buoyant bubbles through a succession of outbursts. We also study the X-ray-cool component detected in the radio lobes and suggest that it is structured in blobs that are tied to the radio buoyant bubbles.

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Section: Introductionmentioning

confidence: 99%

Radiative Cooling and Heating and Thermal Conduction in M87

Ghizzardi

Molendi

Pizzolato

et al. 2004

ApJ

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“…In conclusion, it is clear that a crucial input quantity in determining the value of the HXR excess flux is the detailed modeling of the thermal emission of the IC gas, because different values assumed for the IC gas temperature lead to different conclusions about the amount of HXR excess flux (see, e.g., the long standing discussion about evidence and counter evidence of the HXR excess in Coma, Fusco-Femiano et al 1999, 2004, 2007Rossetti & Molendi 2004, 2007; see also Petrosian et al 2008 for a review). For this reason, it would be extremely important to estimate the temperature of the IC gas with measurements that are independent of those obtained in the X-ray band.…”

Section: Discussionmentioning

confidence: 99%

On the inverse Compton scattering interpretation of the hard X-ray excesses in galaxy clusters: the case of Ophiuchus

Colafrancesco¹,

Marchegiani²

2009

A&A

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Context. Populations of high energy electrons can produce hard X-ray (HXR) emission in galaxy clusters by up-scattering CMB photons via the inverse Compton scattering (ICS) mechanism. However, this scenario has various astrophysical consequences. Aims. We discuss here the consequences of the presence of a population of high energy particles for the multi-frequency emissivity of the same clusters and the structure of their atmospheres. Methods. We derive predictions for the ICS HXR emission in the specific case of the Ophiuchus cluster (for which an interesting combination of observational limits and theoretical scenarios have been presented) for three main scenarios producing high-E electrons: primary cosmic ray model, secondary cosmic rays model and neutralino DM annihilation scenario. We further discuss the predictions of the Warming Ray model for the cluster atmosphere. Under the assumption to fit the HXR emission observed in Ophiuchus, we explore the consequences that these electron populations induce on the cluster atmosphere. Results. We find that: i) primary electrons can be marginally consistent with the available data provided that the electron spectrum is cutoff at E 30 and E 90 MeV for electron spectral index values of 3.5 and 4.4, respectively; ii) secondary electron models from pp collisions are strongly inconsistent with the viable gamma-ray limits, cosmic ray protons produce too much heating of the intracluster (IC) gas and their pressure at the cluster center largely exceeds the thermal one; iii) secondary electron models from DM annihilation are also strongly inconsistent with the viable gamma-ray and radio limits, and electrons produce too much heating of the IC gas at the cluster center, unless the neutralino annihilation cross-section is much lower than the proposed value. In that case, however, these models no longer reproduce the HXR excess in Ophiuchus. Conclusions. We conclude that ICS by secondary electrons from both neutralino DM annihilation and pp collisions cannot be the mechanism responsible for the HXR excess emission; primary electrons are still a marginally viable solution provided that their spectrum has a low-energy cutoff at E 30−90 MeV. We also find that diffuse radio emission localized at the cluster center is expected in all these models and requires quite low values of the average magnetic field (B ∼ 0.1−0.2 μG in primary and secondary-pp models; B ∼ 0.055−0.39 μG in secondary-DM models) to agree with the available observations. Finally, the WR model (with B ∼ 0.4−2.0 μG) offers, so far, the most accurate description of the cluster in terms of the temperature distribution, heating and pressure and multifrequency spectral energy distribution. Fermi observations of Ophiuchus will provide further constraints to this model.

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“…Another method of directly measuring the cluster-wide B-field is from the detection of the inverse Compton (IC) scattered hard X-ray emission in excess of the thermal Bremsstrahlung emission. Recently, excess hard X-ray emission has been detected in the Coma cluster from Beppo-SAX, which gave a cluster B-field of ∼ 0.2µG (Fusco-Femiano et al 1999). However, there are still debates over the origin of the detected hard X-ray excess, with suggestions of it being Bremsstrahlung radiation of supra-thermal electrons (e.g.…”

Section: Intracluster Magnetic Fieldmentioning

confidence: 99%

Diffuse Cluster-Wide Radio Halos

Liang

2002

Highlights astron.

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Abstract. We will discuss the properties and origins of halos and relics including estimates of the cluster magnetic fields, and present results for a few recently discovered halos and relics. The electrons in the suprathermal high energy tail of the thermal gas distribution are likely to provide the seed particles for acceleration through mergers and turbulences to relativistic energies. These relativistic particles are then responsible for the synchrotron emission of the halos.

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Hard X-Ray Radiation in the Coma Cluster Spectrum

Cited by 254 publications

References 33 publications

Radiative Cooling and Heating and Thermal Conduction in M87

Radiative Cooling and Heating and Thermal Conduction in M87

On the inverse Compton scattering interpretation of the hard X-ray excesses in galaxy clusters: the case of Ophiuchus

Diffuse Cluster-Wide Radio Halos

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