The Starburst Contribution to the Extragalactic γ‐Ray Background

Thompson, Todd A.; Quataert, Eliot; Waxman, Eli

doi:10.1086/509068

Cited by 179 publications

(248 citation statements)

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“…It is thus possible that the IGRB emission contains the signature of some of the most powerful and interesting phenomena in astroparticle physics. Intergalactic shocks produced by the assembly of large scale structures (50-52), γ ray emission from galaxy clusters (53,54), and emission from starburst and normal galaxies (55,56) are among the most likely candidates for the generation of diffuse GeV emission. In addition, and most relevant for this review, a signal from dark matter annihilation could be imprinted in the IGRB.…”

Section: Observational Resultsmentioning

confidence: 99%

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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Section: Observational Resultsmentioning

confidence: 99%

Indirect detection of dark matter with γ rays

Funk

2014

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

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“…Other astrophysical sources may emit in the high latitude γ-ray sky: i) radio-quiet AGN [34,35], and Fanaroff and Riley radio galaxies of type I and II [36][37][38] whose contribution is strongly model dependent and likely bound to few percent of the EGB; ii) γ-ray bursts (GRBs), estimated less than 1% of the diffuse extragalactic γ-ray background [39]; iii) star-burst and luminous infrared galaxies. The relevant flux may cover a significant fraction of the EGB (≤ 20%) [40], but the model dependence is such to prevent firm statements on the relevance of this extragalactic source; iv) nearby clusters of galaxies, which could yield about 1% − 10% of the EGRET EGB [41][42][43]; v) gravitational induced shock waves, produced during cluster mergers and large-scale structure formation, whose fluxes are quite model dependent and may reach few percent [44,45]. All these γ-ray sources have been shown to contribute to less than 1% of the Fermi-LAT EGB or to be too highly model dependent.…”

Section: The Extragalactic γ-Ray Backgroundmentioning

confidence: 99%

Conservative upper limits on WIMP annihilation cross section from Fermi-LATγrays

2012

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The spectrum of an isotropic extragalactic γ-ray background (EGB) has been measured by the Fermi-LAT telescope at high latitudes. Two new models for the EGB are derived from the subtraction of unresolved point sources and extragalactic diffuse processes, which could explain from 30% to 70% of the Fermi-LAT EGB. Within the hypothesis that the two residual EGBs are entirely due to the annihilation of dark matter (DM) particles in the Galactic halo, we obtain stringent upper limits on their annihilation cross section. Severe bounds on a possible Sommerfeld enhancement of the annihilation cross section are set as well. Finally, we consider models for DM annihilation depending on the inverse of the velocity and associate the EGBs to photons arising from the annihilation of DM in primordial halos. Given our choices for the EGB and the minimal DM modelling, the derived upper bounds are claimed to be conservative.PACS numbers: 95.30. Cq,95.35+d,95.85.Pw,96.50.sb

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“…It is thus possible that the IGRB emission contains the signature of some of the most powerful and interesting phenomena in astroparticle physics. Intergalactic shocks produced by the assembly of Large Scale Structures (155,156,157), gamma-ray emission from galaxy clusters (158, 159), emission from starburst and normal galaxies (160,161), are among the most likely candidates for the generation of diffuse GeV emission. In addition, a signal from dark matter annihilation could be imprinted in the IGRB.…”

Section: Isotropic Diffuse Emissionmentioning

confidence: 99%

Ground- and Space-Based Gamma-Ray Astronomy

Funk

2015

Annu. Rev. Nucl. Part. Sci.

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In recent years, observational γ-ray astronomy has seen a remarkable range of exciting new results in the high-energy and very-high energy regimes. Coupled with extensive theoretical and phenomenological studies of non-thermal processes in the Universe these observations have provided a deep insight into a number of fundamental problems of high energy astrophysics and astroparticle physics. Although the main motivations of γ-ray astronomy remain unchanged, recent observational results have contributed significantly towards our understanding of many related phenomena. This article aims to review the most important results in the young and rapidly developing field of γ-ray astrophysics.

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The Starburst Contribution to the Extragalactic γ‐Ray Background

Cited by 179 publications

References 68 publications

Indirect detection of dark matter with γ rays

Indirect detection of dark matter with γ rays

Conservative upper limits on WIMP annihilation cross section from Fermi-LATγrays

Ground- and Space-Based Gamma-Ray Astronomy

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