[ITAL]Rossi X-Ray Timing Explorer[/ITAL] Observations of the Coma Cluster

Rephaeli, Yoel; Gruber, D. E.; Blanco, P. R.

doi:10.1086/311828

Cited by 132 publications

(169 citation statements)

References 23 publications

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“…However, in the framework of this model, the EUV excess in Coma should then be interpreted as owing to thermal emission from warm baryons at sub-virial temperature. (Rephaeli et al 1999) and EUVE ). We also report the EGRET (Reimer et al 2003), Fermi (Mori 2009) and HESS (Aharonian et al 2009a) upper limits on Coma.…”

Section: Discussionmentioning

confidence: 99%

Dark matter interpretation of the origin of non-thermal phenomena in galaxy clusters

Colafrancesco

Lieu

Marchegiani

et al. 2011

A&A

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Aims. We studied the multi-frequency predictions of various annihilating dark matter (DM) scenarios in order to explore the possibility to interpret the still unknown origin of non-thermal phenomena in galaxy clusters. Methods. We consider three different DM models with light (9 GeV), intermediate (60 GeV), and high (500 GeV) neutralino mass and study their physical effects in the atmosphere of the Coma cluster. The secondary particles created in the neutralino annihilation processes produce a multi-frequency spectral energy distribution (SED) of non-thermal radiation and also heat the intracluster gas, which we test against the observations available for the Coma cluster from radio to gamma-rays. The various DM-produced SEDs are normalized by the condition to fit the Coma radio halo spectrum, thus obtaining best-fit values of the annihilation cross-section σV and of the central magnetic field B 0 . Results. We find that it is not possible to interpret all the non-thermal phenomena observed in galaxy clusters in terms of DM annihilation. The light-mass DM model with 9 GeV mass produces too little power at all other frequencies, while the high-mass DM model with 500 GeV produces a large excess power at all other frequencies. The intermediate-mass DM model with 60 GeV and τ ± composition is marginally consistent with the HXR and gamma-ray observations, but narrowly fails to reproduce the EUV and soft X-ray observations. The intermediate-mass DM model with 60 GeV and bb composition is, on the other hand, always below the observed fluxes. We note that the radio halo spectrum of Coma is well fitted only in the bb or light-and intermediate-mass DM models. We also find that the heating produced by the DM annihilation in the centre of the Coma cluster is always larger than the intracluster gas cooling rate for an NFW DM density profile and it is substantially smaller than the cooling rate only for a cored DM density profile in light-mass DM model with 9 GeV. Conclusions. The possibility of interpreting the origin of non-thermal phenomena in galaxy clusters with DM annihilation scenarios requires a low neutralino mass and a cored DM density profile. If we then consider the multi-messenger constraints to the neutralino annihilation cross-section, it turns out that this scenario would also be excluded unless we introduce a substantial boost factor that represents DM substructures. If we relax the condition to fit the Coma radio halo and we consider the EUV and HXR detections as upper limits for the non-thermal emission, together with the gamma-ray limit, then the limits on σV are less stringent than those obtained by the multi-messenger analysis.

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Section: Discussionmentioning

confidence: 99%

Dark matter interpretation of the origin of non-thermal phenomena in galaxy clusters

Colafrancesco

Lieu

Marchegiani

et al. 2011

A&A

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“…Up to a few years ago, the search for IC emission in the hard Send offprint requests to: M. Rossetti, e-mail: rossetti@mi.iasf.cnr.it X-ray energy band, the so-called "hard tails", had not met with success (see Rephaeli et al 1987;Rephaeli & Gruber 1998;Henriksen 1998). Recently Fusco-Femiano et al (1999, using BeppoSAX PDS data, and Rephaeli et al (1999) using RXTE data, find evidences for a non-thermal component in the Coma cluster hard X-ray spectrum. Other detections based on BeppoSAX data have been claimed for A2256 (Fusco-Femiano et al 2000) and A754 (Fusco-Femiano et al 2003).…”

Section: Introductionmentioning

confidence: 98%

Is there a hard tail in the Coma Cluster X-ray spectrum?

Rossetti

Molendi

2004

A&A

100

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Abstract.We report results from a re-analysis of the BeppoSAX observation of Coma and from the analysis of a second, yet unpublished observation of the same object. From our re-analysis of the first observation we find that the statistical evidence for a hard tail is about 2σ. From the analysis of the second observation which, thanks to the lower background and the longer exposure time, is characterized by a larger signal-to-noise we find no evidence for a hard tail. From the upper limit on the flux of the hard tail, using the standard Inverse Compton formulae, we derive a lower limit for the magnetic of ∼0.2−0.4 µGauss consistent with Faraday rotation measurements.

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“…outside the core of X-ray clusters), the magnetic field is expected to make only a small contribution to the total pressure. The typical values for our predicted IGMF at the mean IGM density translate to a mixed magnetic field strength of ∼ 0.15 √ −1 µG (∼ 1.5 √ −1 µG) at an overdensity of ∼ 10 3 in the RLQ (BALQSO) model, comparable to the inferred field amplitude on Mpc scales around X-ray clusters (Fusco-Femiano et al 1999;Rephaeli et al 1999;Kaastra et al 1999;Kim et al 1989). The most important unknown parameter in our model is B , the ratio of magnetic to kinetic energy in quasar outflows.…”

Section: Discussionsupporting

confidence: 73%

“…Substantial magnetic fields are also known to exist on larger cosmological scales but their dynamical significance is uncertain. Faraday rotation measurements imply a lower limit of 1-100 µG on the tangled magnetic field in the cores of X-ray clusters (Kim et al 1990(Kim et al , 1991Taylor & Perley 1993;Ge & Owen 1993;Dreher et al 1987;Perley & Taylor 1991), while the comparison between the synchrotron and inverse-Compton emission by relativistic electrons in the outer ( ∼ > 1 Mpc) envelopes of X-ray clusters indicates a lower limit of ∼ 0.1 µG there (Fusco-Femiano et al 1999;Rephaeli et al 1999;Kaastra et al 1999;Kim et al 1989). The observed field amplitude of B ∼ > 10 −7 G in collapsed environments with an overdensity factor of δ ∼ 10 3 translates to B ∼ > 10 −9 G at the mean density of the intergalactic medium (IGM), under the assumption that the field was adiabatically compressed (B ∝ δ 2/3 ) as the gas collapsed.…”

Section: Introductionmentioning

confidence: 99%

Intergalactic Magnetic Fields from Quasar Outflows

Furlanetto

Loeb

Eso Astrophysics Symposia

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Outflows from quasars inevitably pollute the intergalactic medium (IGM) with magnetic fields. The short-lived activity of a quasar leaves behind an expanding magnetized bubble in the IGM. We model the expansion of the remnant quasar bubbles and calculate their distribution as a function of size and magnetic field strength at different redshifts. We generically find that by a redshift z ∼ 3, about 5-20% of the IGM volume is filled by magnetic fields with an energy density ∼ > 10% of the mean thermal energy density of a photo-ionized IGM (at ∼ 10 4 K). As massive galaxies and X-ray clusters condense out of the magnetized IGM, the adiabatic compression of the magnetic field could result in the field strength observed in these systems without a need for further dynamo amplification. The intergalactic magnetic field could also provide a nonthermal contribution to the pressure of the photo-ionized gas that may account for the claimed discrepancy between the simulated and observed Doppler width distributions of the Lyα forest.

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[ITAL]Rossi X-Ray Timing Explorer[/ITAL] Observations of the Coma Cluster

Cited by 132 publications

References 23 publications

Dark matter interpretation of the origin of non-thermal phenomena in galaxy clusters

Dark matter interpretation of the origin of non-thermal phenomena in galaxy clusters

Is there a hard tail in the Coma Cluster X-ray spectrum?

Intergalactic Magnetic Fields from Quasar Outflows

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