UHECR observations and lensing in the magnetic field of the Virgo cluster

Dolag, K.; Kachelrieß, M.; Semikoz, D.

doi:10.1088/1475-7516/2009/01/033

Cited by 36 publications

(44 citation statements)

References 42 publications

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“…[44], even if there is only one source in the Virgo galaxy cluster, the cluster should shine as a whole due to substantial deflections of UHECRs in the magnetic fields inside. This means that the Virgo cluster can be considered as an extended source, basically a ' 5 radius disk on the celestial sphere.…”

Section: Discussionmentioning

confidence: 99%

“…The uncertainties due to the fit are of the order of $10 , because of the low energy ordering of events in the Cen A region. Moreover, even if M87 would be the only source in Virgo, the magnetic fields in the cluster can be sufficient to significantly deflect trajectories of UHE heavy nuclei inside and make whole cluster shine as an extended source [44].…”

Section: Application To the Data Of The Pierre Auger Observatorymentioning

confidence: 99%

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Method to look for imprints of ultrahigh energy nuclei sources

Giacinti

Semikoz

2011

Phys. Rev. D

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We propose a new method to search for heavy nuclei sources, on top of background, in the Ultra-High Energy Cosmic Ray data. We apply this method to the 69 events recently published by the Pierre Auger Collaboration [P. Abreu et al. (Pierre Auger Observatory Collaboration), Astropart. Phys. 34, 314 (2010).] and find a tail of events for which it reconstructs the source at a few degrees from the Virgo galaxy cluster. The reconstructed source is located at ' 8:5 from M87. The probability to have such a cluster of events in some random background and reconstruct the source position in any direction of the sky is about 7 Â 10 À3 . The probability to reconstruct the source at less than 10 from M87 in a data set already containing such a cluster of events is about 4 Â 10 À3 . This may be a hint at the Virgo cluster as a bright ultrahigh energy nuclei source. We investigate the ability of current and future experiments to validate or rule out this possibility, and discuss several alternative solutions which could explain the existing anisotropy in the Auger data.

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Section: Discussionmentioning

confidence: 99%

Section: Application To the Data Of The Pierre Auger Observatorymentioning

confidence: 99%

Method to look for imprints of ultrahigh energy nuclei sources

Giacinti

Semikoz

2011

Phys. Rev. D

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“…(i) We assumed a simple scaling of the magnetic energy density with the thermal energy density that allows us to effectively scan the observationally allowed parameter space for the magnetic field. Note that current SPH implementations that are capable of following MHD are presently still fraught with numerical and physical difficulties, in particular when following dissipative gas physics (Dolag, Bartelmann & Lesch 1999;Price & Monaghan 2004;Dolag et al 2005;Price & Monaghan 2005). While the IC and pion-decay emission are mostly independent of the magnetic field, our synchrotron maps might be modified when the MHD is properly accounted for.…”

Section: Limitations and Future Workmentioning

confidence: 99%

Simulating cosmic rays in clusters of galaxies – II. A unified scheme for radio haloes and relics with predictions of the γ-ray emission

Pfrommer

Enßlin

Springel

2008

Monthly Notices RAS

181

272

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The thermal plasma of galaxy clusters lost most of its information on how structure formation proceeded as a result of dissipative processes. In contrast, non‐equilibrium distributions of cosmic rays (CRs) preserve the information about their injection and transport processes and provide thus a unique window of current and past structure formation processes. This information can be unveiled by observations of non‐thermal radiative processes, including radio synchrotron, hard X‐ray and γ‐ray emission. To explore this, we use high‐resolution simulations of a sample of galaxy clusters spanning a mass range of about two orders of magnitudes, and follow self‐consistent CR physics on top of the radiative hydrodynamics. We model relativistic electrons that are accelerated at cosmological structure formation shocks and those that are produced in hadronic interactions of CRs with ambient gas protons. We find that the CR proton pressure traces the time integrated non‐equilibrium activities of clusters and is modulated by the recent dynamical activities. In contrast, the pressure of primary shock‐accelerated CR electrons resembles current accretion and merging shock waves that break at the shallow cluster potential in the virial regions. The resulting synchrotron emission is predicted to be polarized and has an inhomogeneous and aspherical spatial distribution which matches the properties of observed radio relics. We propose a unified scheme for the generation of giant radio haloes as well as radio minihaloes that naturally arises from our simulated synchrotron surface brightness maps and emission profiles. Giant radio haloes are dominated in the centre by secondary synchrotron emission with a transition to the radio synchrotron radiation emitted from primary, shock‐accelerated electrons in the cluster periphery. This model is able to explain the regular structure of radio haloes by the dominant contribution of hadronically produced electrons. At the same time, it is able to account for the observed correlation of mergers with radio haloes, the larger peripheral variation of the spectral index, and the large scatter in the scaling relation between cluster mass and synchrotron emission. Future low‐frequency radio telescopes (LOFAR, GMRT, MWA, LWA) are expected to probe the accretion shock regions of clusters and the warm–hot intergalactic medium, depending on the adopted model for the magnetic fields. The hadronic origin of radio haloes can be scrutinized by the detection of pion‐decay‐induced γ‐rays following hadronic CR interactions. The high‐energy γ‐ray emission depends only weakly on whether radiative or non‐radiative gas physics is simulated due to the self‐regulated nature of the CR cooling processes. Our models predict a γ‐ray emission level that should be observable with the GLAST satellite.

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“…Even in the case the cluster would contain only one source, deflections by magnetic fields inside the cluster lead to an extended source [46]. For the galaxy cluster images, we also assume that deflections of UHECR nuclei in extragalactic magnetic fields are weak enough (as in, e.g.…”

Section: Qualitative Consequences Of Deflections In the Turbulent Gmfmentioning

confidence: 99%

Ultrahigh energy nuclei in the turbulent Galactic magnetic field

Giacinti

Kachelrieß

Semikoz

et al. 2011

Astroparticle Physics

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In this work we study how the turbulent component of the Galactic magnetic field (GMF) affects the propagation of ultrahigh energy heavy nuclei. We investigate first how the images of individual sources and of the supergalactic plane depend on the properties of the turbulent GMF. Then we present a quantitative study of the impact of the turbulent field on (de-) magnification of source fluxes, due to magnetic lensing effects. We also show that it is impossible to explain the Pierre Auger data assuming that all ultrahigh energy nuclei are coming from Cen A, even in the most favorable case of a strong, extended turbulent field in the Galactic halo.

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UHECR observations and lensing in the magnetic field of the Virgo cluster

Cited by 36 publications

References 42 publications

Method to look for imprints of ultrahigh energy nuclei sources

Method to look for imprints of ultrahigh energy nuclei sources

Simulating cosmic rays in clusters of galaxies – II. A unified scheme for radio haloes and relics with predictions of the γ-ray emission

Ultrahigh energy nuclei in the turbulent Galactic magnetic field

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