Effect of turbulent reacceleration on electrons produced by dark matter annihilation in the Coma cluster

Marchegiani, ¶.

doi:10.1093/mnras/stz1798

Cited by 4 publications

(2 citation statements)

References 55 publications

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Section: Transport Modelmentioning

confidence: 99%

Universal profiles for radio searches of Dark Matter in dwarf galaxies

Vollmann

2021

J. Cosmol. Astropart. Phys.

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The phenomenology of diffuse radio emission from Dark Matter annihilation or decay in dwarf spheroidal galaxies is examined. We introduce (in the context of cosmic-ray physics) a novel strategy for the computation of the relevant synchrotron signals. In particular, we identify various regimes where, in analogy to prompt gamma rays, the diffuse radio signal from dark matter annihilation/decay can be expressed as the multiplication of a halo times a spectral function. These functions are computed here for the first time for a number of benchmark cases. Furthermore, we find parameter regions in which the emissivity can be well approximated by a universal function ∼ sin(π r/r h)/r, where r is the galacto-centric distance and r h the diffusion-zone radius of the galaxy. Our theoretical setup differs from previous work in that, instead of employing a method-of-images strategy, we consider a Fourier-mode expansion of the relevant Green's functions. With this strategy, exact results can be obtained with very low computational cost and for generic dark matter models. In particular, 𝒪(10–100) Fourier modes can be easily incorporated into the computations in order to probe the smallest scales of the problem. We also propose a new strategy to search for dark matter using radio observations of dwarf galaxies that is (1) easy to implement and (2) free of the otherwise large degeneracies in the description of synchrotron signals from dark matter. Finally, we correct a mistake in a widely used Green's function formula in this context. We show that the original expression leads to systematically incorrect — and in some cases divergent — results in the regime where the characteristic time-scale for diffusion is smaller than that for energy losses.

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Section: Transport Modelmentioning

confidence: 99%

Universal profiles for radio searches of Dark Matter in dwarf galaxies

Vollmann

2021

J. Cosmol. Astropart. Phys.

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“…We thus assume stationarity, spherical symmetry and isotropic momentum distribution: all terms in the equation can only depend on the galactocentric distance, r, and the energy, E, of the CREs. See [74] for a discussion on reacceleration effects in clusters of galaxies and why these are irrelevant in dSphs. The validity of the stationarity is further discussed below in II D. A stronger assumption is the fact that the energy-losses and diffusion coefficients do not depend on the galactocentric distance r. This assumption which is also adopted in conventional CR transport models in the MW [72], is closely related to the constancy of the large-scale magnetic field within the diffusive volume of the galaxy.…”

Section: A Transport Modelmentioning

confidence: 99%

Universal profiles for radio searches of dark matter in dwarf galaxies

Vollmann

2020

Preprint

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The phenomenology of diffuse radio emission from Dark Matter annihilation or decay in dwarf spheroidal galaxies is examined. We introduce (in the context of cosmic-ray physics) a novel strategy for the computation of the relevant synchrotron signals. In particular, we identify various regimes where, in analogy to prompt gamma rays, the diffuse radio signal from dark matter annihilation/decay can be expressed as the multiplication of a halo times a spectral function. These functions are computed here for the first time for a number of benchmark cases. Furthermore, we find parameter regions in which the emissivity can be well approximated by a universal function ∼ sin(πr/r h )/r, where r is the galacto-centric distance and r h the diffusion-zone radius of the galaxy. Our theoretical setup differs from previous work in that, instead of employing a method-of-images strategy, we consider a Fourier-mode expansion of the relevant Green's functions. With this strategy, exact results can be obtained with very low computational cost and for generic dark matter models. In particular, O(10 -100) Fourier modes can be easily incorporated into the computations in order to probe the smallest scales of the problem. We also propose a new strategy to search for dark matter using radio observations of dwarf galaxies that is (1) easy to implement and (2) free of the otherwise large degeneracies in the description of synchrotron signals from dark matter. Finally, we correct a mistake in a widely used Green's function formula in this context. We show that the original expression leads to systematically incorrect -and in some cases divergent -results in the regime where the characteristic time-scale for diffusion is smaller than that for energy losses.

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An excess radio signal in the Abell 4038 cluster

Chan

Lee

2020

Monthly Notices of the Royal Astronomical Society

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In the past decade, some telescopes (e.g. Fermi-LAT, AMS and DAMPE) were launched to detect the signals of annihilating dark matter in our Galaxy. Although some excess of gamma rays, anti-protons and electrons/positrons have been reported and claimed as dark matter signals, the uncertainties of Galactic pulsars’ contributions are still too large to confirm the claims. In this article, we report a possible radio signal of annihilating dark matter manifested in the archival radio continuum spectral data of the Abell 4038 cluster. By assuming the thermal annihilation cross section and comparing the dark matter annihilation model with the null hypothesis (cosmic ray emission without dark matter annihilation), we get very large Test Statistic values TS >45 for four popular annihilation channels, which correspond to more than 6σ statistical preference. This reveals a possible potential signal of annihilating dark matter. In particular, our results are also consistent with the recent claims of dark matter mass m ≈ 30 − 50 GeV annihilating via the $b\bar{b}$ quark channel with the thermal annihilation cross section. However, we cannot, at this time, exclude the possibility that a better background cosmic-ray model could explain the spectral data without recourse to dark matter annihilations.

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Effect of turbulent reacceleration on electrons produced by dark matter annihilation in the Coma cluster

Cited by 4 publications

References 55 publications

Universal profiles for radio searches of Dark Matter in dwarf galaxies

Universal profiles for radio searches of Dark Matter in dwarf galaxies

Universal profiles for radio searches of dark matter in dwarf galaxies

An excess radio signal in the Abell 4038 cluster

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