The COMPTEL instrumental-line background

Abstract. We calculate the extragalactic diffuse emission originating from the upscattering of cosmic microwave photons by energetic electrons and positrons produced in particle dark matter annihilation events at all redshifts and in all halos. We outline the observational constraints on this emission and we study its dependence on both the particle dark matter model (including the particle mass and its dominant annihilation final state) and on assumptions on structure formation and on the density profile of halos. We find that for low-mass dark matter models, data in the X-ray band provide the most stringent constraints, while the gamma-ray energy range probes models featuring large masses and pair-annihilation rates, and a hard spectrum for the injected electrons and positrons. Specifically, we point out that the all-redshift, all-halo inverse Compton emission from many dark matter models that might provide an explanation to the anomalous positron fraction measured by the Pamela payload severely overproduces the observed extragalactic gamma-ray background.

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“…The data shown are from Ref. [51] (Chandra), [54] (Swift ), [58] (Comptel ), [60,61] (EGRET), and the model for hard X-ray AGN is from Ref. [55].…”

Section: Resultsmentioning

confidence: 99%

“…However, a significant extragalactic background is observed in the MeV [58,59] and GeV range [60,61]. Here blazars may make a significant contribution and under reasonable assumptions can account for the entire MeV background [57].…”

Section: Overview Of Observational Datamentioning

confidence: 99%

Extragalactic Inverse Compton Light from Dark Matter annihilation and the Pamela positron excess

Profumo

Jeltema

2009

J. Cosmol. Astropart. Phys.

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“…∼ 0, that for all the models we consider is quite a good approximation at the present time z = 0, where the clumping factor reaches its maximum value). We use to this purpose the measurements of the diffuse gammaray background in the 1 MeV -100 GeV range conducted by EGRET [87,88] and COMPTEL [89], and those of the diffuse x-ray background in the sub-MeV range conducted by the SPI spectrometer aboard INTEGRAL [90].…”

Section: Resultsmentioning

confidence: 99%

Signatures of clumpy dark matter in the global 21 cm background signal

Cumberbatch

Lattanzi

Silk³

2010

Phys. Rev. D

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We examine the extent to which the self-annihilation of supersymmetric neutralino dark matter, as well as light dark matter, influences the rate of heating, ionisation and Lyman-α pumping of interstellar hydrogen and helium and the extent to which this is manifested in the 21 cm global background signal. We fully consider the enhancements to the annihilation rate from DM halos and substructures within them. We find that the influence of such structures can result in significant changes in the differential brightness temperature, δT b . The changes at redsfhits z < 25 are likely to be undetectable due to the presence of the astrophysical signal; however, in the most favourable cases, deviations in δT b , relative to its value in the absence of self-annihilating DM, of up to ≃ 20 mK at z = 30 can occur. Thus we conclude that, in order to exclude these models, experiments measuring the global 21 cm signal, such as EDGES and CORE, will need to reduce the systematics at 50 MHz to below 20 mK.PACS numbers: 95.35+d

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“…The accumulated and redshifted !-ray line spectra form a continuum, with its normalization and spectral features probing the rate and redshift evolution of the contributing SN Ia. While both COMPTEL and SMM measured a !-ray continuum in the MeV region [116,115], it was unclear if it could be associated with the expected SN Ia signal [114,95]. The normalization of the SN Ia prediction was quite uncertain, and the data were not precise enough to conclusively test for the expected spectral features.…”

Section: Sne Ia Rate-cosmic Gamma-ray Backgroundmentioning

confidence: 99%