Gamma-ray line emission from galaxy clusters

Iyudin, A. F.; Böhringer, H.; Dogiel, V. A.; Morfill, Gregor

doi:10.1051/0004-6361:20031599

Cited by 9 publications

(8 citation statements)

References 60 publications

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“…These X-rays are accompanied by the excitation of background nuclei which could be detectable through the development of prominent carbon and oxygen gamma-ray lines. Dogiel (2001) subrelativistic protons estimated by Iyudin et al (2004) is of the order of ∼8 × 10 48 erg s −1 , which matches the required rate if protons produce the observed hard X-ray flux (Dogiel 2001). However, this process involves subrelativistic protons and so it faces the same problem of energetics and plasma heating as we discussed in Sect.…”

Section: The Spectrum Of Accelerated Protonssupporting

confidence: 73%

In-situ acceleration of subrelativistic electrons in the Coma halo and the halo's influence on the Sunyaev-Zeldovich effect

Dogiel

Colafrancesco

et al. 2006

A&A

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Aims. The stochastic acceleration of subrelativistic electrons from a background plasma is studied in order to find a possible explanation of the hard X-ray emission detected from the Coma cluster. Methods. We calculate the necessary energy supply as a function of the plasma temperature and of the electron energy, and we show that, for the same value of the hard X-ray flux, the energy supply changes gradually from its high value for the case when emitting particle are non-thermal to lower values when the electrons are thermal. The kinetic equations we use include terms describing particle thermalization as well as momentum diffusion due to the Fermi II acceleration. Results. We show that the temporal evolution of the particle distribution function has, at its final stationary stage, a rather specific form. This distribution function cannot be described by simple exponential or power-law expressions. A broad transfer region is formed by Coulomb collisions at energies between the Maxwellian and power-law parts of the distribution functions. In this region the radiative lifetime of a single quasi-thermal electron differs greatly from the lifetime of the distribution function as a whole. For a plasma temperature of 8 keV, the particles emitting bremsstrahlung at 20−80 keV lie in this quasi-thermal regime. We show that the energy supply required by quasi-thermal electrons to produce the observed hard X-ray flux from Coma is one or two orders of magnitude smaller than the value derived from the assumption of a nonthermal origin of the emitting particles. This result may solve the problem of rapid cluster overheating by nonthermal electrons raised by Petrosian (2001): while Petrosian's estimates are correct for nonthermal particles, they are inapplicable in the quasi-thermal range. We finally analyze the change in Coma's Sunyaev-Zeldovich effect caused by the implied distortions of the Maxwellian spectrum of electrons, and we show that evidence for the acceleration of subrelativistic electrons can, in principle, be derived from detailed spectral measurements.

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Section: The Spectrum Of Accelerated Protonssupporting

confidence: 73%

In-situ acceleration of subrelativistic electrons in the Coma halo and the halo's influence on the Sunyaev-Zeldovich effect

Dogiel

Colafrancesco

et al. 2006

A&A

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“…No significant variation of the line flux value was detected during ∼6 years exposure of this excess, which excludes its possible association with the exponentially decaying 22 Na. The absence of the expected strong line at 4.4 MeV from the Aquila excess is explained by the difficulty in handling the large instrumental background around this line (see Iyudin et al 2004).…”

Section: The Aquila Excessmentioning

confidence: 99%

Global Galactic distribution of the 1.275 MeV γ-ray line emission

Iyudin

Bennett

Lichti

et al. 2005

A&A

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We present results of the analysis of 1.275 MeV γ-ray line global distribution derived from the all-sky data accumulated by COMPTEL on board the Compton Gamma Ray Observatory (CGRO) from 1991 to 1997. Previously the 1.275 MeV γ-ray line was believed to be largely produced in the decay of radioactive isotope 22 Na that is synthesised in the classical nova (CN) thermonuclear runaway (TNR). Another way to produce the 1.275 MeV line emission is via the excitation of 22 Ne-nuclei, e.g. through the low-energy cosmic ray interactions with the nuclei of the interstellar matter that lead to the production of 22 Ne * , or of 22 Na. This scenario, as we now believe, can be dominant in contributing to the total 1.275 MeV γ-ray line emission from the galactic bulge. Unfortunately, systematic uncertainties in the analysis of the COMPTEL data hinder a clear distinction between two alternative scenarios.

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“…These secondary CRe would generate radio halos through synchrotron emission (Dennison 1980;Vestrand 1982;Blasi & Colafrancesco 1999;Dolag & Enßlin 2000;Pfrommer & Enßlin 2004). This scenario is motivated by the 1 Indeed, there are first hints for the existence of a 10 MeV -100 MeV CRp population deriving from the detection of excited gamma-ray lines from the clusters Coma and Virgo (Iyudin et al 2004). If verified, that would make a high energy (GeV) CRp population very plausible.…”

Section: Introductionmentioning

confidence: 99%

“…1 1 Indeed, there are first hints for the existence of a 10–100 MeV CRp population deriving from the detection of excited gamma‐ray lines from the clusters Coma and Virgo (Iyudin et al 2004). If verified, that would make a high‐energy (GeV) CRp population very plausible. …”

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confidence: 99%

Estimating galaxy cluster magnetic fields by the classical and hadronic minimum energy criterion

Pfrommer

Enßlin

2004

Monthly Notices of the Royal Astronomical Society

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We wish to estimate magnetic field strengths of radio emitting galaxy clusters by minimizing the non‐thermal energy density contained in cosmic ray electrons (CRe), protons (CRp), and magnetic fields. The classical minimum energy estimate can be constructed independently of the origin of the radio synchrotron emitting CRe yielding thus an absolute minimum of the non‐thermal energy density. Provided the observed synchrotron emission is generated by a CRe population originating from hadronic interactions of CRp with the ambient thermal gas of the intra‐cluster medium, the parameter space of the classical scenario can be tightened by means of the hadronic minimum energy criterion. For both approaches, we derive the theoretically expected tolerance regions for the inferred minimum energy densities. Application to the radio halo of the Coma cluster and the radio mini‐halo of the Perseus cluster yields equipartition between cosmic rays and magnetic fields within the expected tolerance regions. In the hadronic scenario, the inferred central magnetic field strength ranges from 2.4 μG (Coma) to 8.8 μG (Perseus), while the optimal CRp energy density is constrained to 2 per cent ± 1 per cent of the thermal energy density (Perseus). We discuss the possibility of a hadronic origin of the Coma radio halo while current observations favour such a scenario for the Perseus radio mini‐halo. Combining future expected detections of radio synchrotron, hard X‐ray inverse Compton, and hadronically induced γ‐ray emission should allow an estimate of volume averaged cluster magnetic fields and provide information about their dynamical state.

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Gamma-ray line emission from galaxy clusters

Cited by 9 publications

References 60 publications

In-situ acceleration of subrelativistic electrons in the Coma halo and the halo's influence on the Sunyaev-Zeldovich effect

In-situ acceleration of subrelativistic electrons in the Coma halo and the halo's influence on the Sunyaev-Zeldovich effect

Global Galactic distribution of the 1.275 MeV γ-ray line emission

Estimating galaxy cluster magnetic fields by the classical and hadronic minimum energy criterion

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