The isotropic radio background and annihilating dark matter

Hooper, Dan; Belikov, Alexander V.; Jeltema, T.; Linden, Tim; Profumo, Stefano; Slatyer, Tracy R.

doi:10.1103/physrevd.86.103003

Cited by 49 publications

(73 citation statements)

References 94 publications

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“…A thorough examination of the spectral models which fit the ARCADE-2 excess has already been presented in Hooper et al [46]. However, different spectral models also produce different anisotropies through their effect on the total dark matter flux above 4 GHz in models that are similarly normalized to fit the ARCADE-2 excess at lower frequencies.…”

Section: Resultsmentioning

confidence: 99%

“…We then scale the boost factor by M 0. 39 halo for larger and smaller halos [46]. We note that the contribution from dark matter substructure can extend well beyond the virial radius of the host halo [47][48][49].…”

Section: A the Synchrotron Anisotropy Calculationmentioning

confidence: 99%

“…The latter magnetic field is added to account for the large magnetic fields observed in the center of the Milky Way galaxy [53]. We note that these radial values are given by the best fit radial profiles to those models adopted in [46].…”

Section: Magnetic Fieldsmentioning

confidence: 99%

“…In order to calculate the contribution from cluster-sized halos, which we define here to consist of halos greater than 2 × 10 12 M , we adopt the same formalism as in [46] which gives the magnetic field as a function of the radial distance from the center of the cluster to be:…”

Section: Magnetic Fieldsmentioning

confidence: 99%

“…The steady state distribution of the e + e − injected via dark matter annihilation can be solved using the conti-nuity equation [46]:…”

Section: Synchrotron Spectral Modelsmentioning

confidence: 99%

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Anisotropy of the extragalactic radio background from dark matter annihilation

Fang

Linden

2015

Phys. Rev. D

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Observations of the extragalactic radio background have uncovered a significant isotropic emission across multiple frequencies spanning from 22 MHz to 10 GHz. The intensity of this non-thermal emission component significantly exceeds the expected contribution from known astrophysical sources. Interestingly, models have indicated that the annihilation of dark matter particles may reproduce both the flux and spectrum of the excess. However, the lack of a measurable anisotropy in the residual emission remains challenging for both dark matter and standard astrophysical interpretations of the ARCADE-2 data. We calculate the expected synchrotron anisotropy from dark matter annihilation and show that these models can produce very small anisotropies, though this requires galaxy clusters to have large substructure contributions and strong magnetic fields. We show that this constraint can be significantly relaxed, however, in scenarios where electrons produced via dark matter annihilation can be efficiently reaccelerated by Alfvén waves in the intra-Cluster medium. Our analysis indicates that any source capable of explaining the intensity and isotropy of the extragalactic radio excess must have a spatial extension far larger than typical for baryons in galaxies, hinting at a novel physics interpretation.

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Section: Resultsmentioning

confidence: 99%

Section: A the Synchrotron Anisotropy Calculationmentioning

confidence: 99%

Section: Magnetic Fieldsmentioning

confidence: 99%

Section: Magnetic Fieldsmentioning

confidence: 99%

“…The steady state distribution of the e + e − injected via dark matter annihilation can be solved using the conti-nuity equation [46]:…”

Section: Synchrotron Spectral Modelsmentioning

confidence: 99%

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Anisotropy of the extragalactic radio background from dark matter annihilation

Fang

Linden

2015

Phys. Rev. D

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Two emission mechanisms in the Fermi Bubbles: A possible signal of annihilating dark matter

Slatyer

2013

Physics of the Dark Universe

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324

408

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We study the variation of the spectrum of the Fermi Bubbles with Galactic latitude. Far from the Galactic plane (|b| > ∼ 30 • ), the observed gamma-ray emission is nearly invariant with latitude, and is consistent with arising from inverse Compton scattering of the interstellar radiation field by cosmicray electrons with an approximately power-law spectrum. The same electrons in the presence of microgauss-scale magnetic fields can also generate the the observed microwave "haze". At lower latitudes (|b| < ∼ 20 • ), in contrast, the spectrum of the emission correlated with the Bubbles possesses a pronounced spectral feature peaking at ∼1-4 GeV (in E 2 dN/dE) which cannot be generated by any realistic spectrum of electrons. Instead, we conclude that a second (non-inverse-Compton) emission mechanism must be responsible for the bulk of the low-energy, low-latitude emission. This second component is spectrally similar to the excess GeV emission previously reported from the Galactic Center (GC), and also appears spatially consistent with a luminosity per volume falling approximately as r −2.4 , where r is the distance from the GC. Consequently, we argue that the spectral feature visible in the low-latitude Bubbles is most likely the extended counterpart of the GC excess, now detected out to at least ∼2-3 kpc from the GC. The spectrum and angular distribution of the signal is broadly consistent with that predicted from ∼10 GeV dark matter particles annihilating to leptons, or from ∼50 GeV dark matter particles annihilating to quarks, following a distribution similar to, but slightly steeper than, the canonical Navarro-Frenk-White (NFW) profile. We also consider millisecond pulsars as a possible astrophysical explanation for the signal, as observed millisecond pulsars possess a spectral cutoff at approximately the required energy. Any such scenario would require a large population of unresolved millisecond pulsars extending at least 2-3 kpc from the GC. PACS numbers: 95.85.Pw, 98.70.Rz, 95.35.+d 1 The dataset we employ may be downloaded from http://heasarc.gsfc.nasa.gov/FTP/fermi/data/lat/weekly.

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Indirect detection of dark matter with γ rays

Funk

2014

Proc. Natl. Acad. Sci. U.S.A.

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The details of what constitutes the majority of the mass that makes up dark matter in the Universe remains one of the prime puzzles of cosmology and particle physics today-80 y after the first observational indications. Today, it is widely accepted that dark matter exists and that it is very likely composed of elementary particles, which are weakly interacting and massive [weakly interacting massive particles (WIMPs)]. As important as dark matter is in our understanding of cosmology, the detection of these particles has thus far been elusive. Their primary properties such as mass and interaction cross sections are still unknown. Indirect detection searches for the products of WIMP annihilation or decay. This is generally done through observations of γ-ray photons or cosmic rays. Instruments such as the Fermi large-area telescope, high-energy stereoscopic system, major atmospheric gamma-ray imaging Cherenkov, and very energetic radiation imaging telescope array, combined with the future Cherenkov telescope array, will provide important complementarity to other search techniques. Given the expected sensitivities of all search techniques, we are at a stage where the WIMP scenario is facing stringent tests, and it can be expected that WIMPs will be either be detected or the scenario will be so severely constrained that it will have to be rethought. In this sense, we are on the threshold of discovery. In this article, I will give a general overview of the current status and future expectations for indirect searches of dark matter (WIMP) particles.T here is a broad consensus that dark matter (DM) is made up of elementary particles. The most promising candidates are weakly interacting massive particles (WIMPs), particularly if they also form the lightest supersymmetric particle. The general assumption is that the thermal freeze-out in the early Universe leaves a relic density of dark matter particles in the current Universe (after the freeze-out, the particles become too diluted to annihilate in appreciable numbers and thermal energies were too low to produce them; the comoving density is therefore roughly constant since then). The annihilation of these particles into standard model particles controls the abundance in the Universe; thus, there is a tight connection between the annihilation cross section and cosmologically relevant quantities. For particles annihilating (in the simplest case, i.e., annihilating through S waves) (1), the relic density only depends on the annihilation cross section σ ann weighted by the average velocity of the particle (2) Ω χ h 2 = 0:11 3 × 10 −26 cm 3 · s −1 hσ ann vi :As the value for the relic dark matter density from cosmic microwave background (CMB) observations is Ω χ h 2 = 0:113 ± 0:004 (3), it follows that the expected velocity-weighted annihilation cross section is in the range of 3 × 10 −26 cm 3 · s −1 . This represents a striking connection that for typical gauge couplings to ordinary standard model particles and a dark matter mass at the weak interaction scale, WIMPs have the...

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The isotropic radio background and annihilating dark matter

Cited by 49 publications

References 94 publications

Anisotropy of the extragalactic radio background from dark matter annihilation

Anisotropy of the extragalactic radio background from dark matter annihilation

Two emission mechanisms in the Fermi Bubbles: A possible signal of annihilating dark matter

Indirect detection of dark matter with γ rays

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