Early SPI/INTEGRAL constraints on the morphology   of the 511 keV 
line emission in the 4th galactic quadrant

Knödlseder, J.; Lonjou, V.; Jean, P.; Allain, Marc; Mandrou, P.; Roques, J. P.; Skinner, G.; Védrenne, G.; Ballmoos, P. von; Weidenspointner, G.; Caraveo, P. A.; Cordier, B.; Schönfelder, V.; Teegarden, B. J.

doi:10.1051/0004-6361:20031437

Cited by 162 publications

(162 citation statements)

References 19 publications

(34 reference statements)

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“…• Knödlseder et al 2003). Generally only the sum of the components are presented since the separate components do not necessarily have physical significance; the idea is to include sufficient aspects of Galactic structure to be able to reproduce the total emission with reasonable confidence.…”

Section: Diffuse Galactic Emissionmentioning

confidence: 99%

Gamma-ray continuum emission from the inner Galactic region as observed with INTEGRAL/SPI

Strong¹,

Diehl²,

Halloin³

et al. 2005

A&A

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117

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The diffuse continuum emission from the Galactic plane in the energy range 18-1000 keV has been studied using 16 Ms of data from the SPI instrument on INTEGRAL. With such an exposure we can exploit the imaging properties of SPI to achieve a good separation of point sources from the various diffuse components. Using a candidate-source catalogue derived with IBIS on INTEGRAL and a number of sky distribution models we obtained spectra resolved in Galactic longitude. We can identify spectral components of a diffuse continuum of power law shape with index about 1.7, a positron annihilation component with a continuum from positronium and the line at 511 keV, and a second, roughly power-law component from detected point sources. Our analysis confirms the concentration of positron annihilation emission in the inner region (|l| < 10• ), the disk (10 • < |l| < 30• ) being at least a factor 7 weaker in this emission. The power-law component in contrast drops by only a factor 2, showing a quite different longitude distribution and spatial origin. Detectable sources constitute about 90% of the total Galactic emission between 20 and 60 keV, but have a steeper spectrum than the diffuse emission, their contribution to the total emission dropping rapidly to a small fraction at higher energies. The spectrum of diffuse emission is compatible with RXTE and COMPTEL at lower and higher energies respectively. In the SPI energy range the flux is lower than found by OSSE, probably due to the more complete accounting for sources by SPI. The power-law emission is difficult to explain as of interstellar origin, inverse Compton giving at most 10%, and instead a population of unresolved point sources is proposed as a possible origin, AXPs with their spectral hardening above 100 keV being plausible candidates. We present a broadband spectrum of the Galactic emission from 10 keV to 100 GeV.

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Section: Diffuse Galactic Emissionmentioning

confidence: 99%

Gamma-ray continuum emission from the inner Galactic region as observed with INTEGRAL/SPI

Strong¹,

Diehl²,

Halloin³

et al. 2005

A&A

Self Cite

117

100

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“…Furthermore, the recent observation, by the INTE-GRAL satellite, of a 511 keV diffuse emission line from the galactic bulge [8] shows that electron-positron anni- [6] (we remove the error bars for sake of visibility). The crosses (HEAO), stars (COMPTEL) and diamonds (EGRET) correspond to the observations [1,2].…”

Section: Introductionmentioning

confidence: 99%

Soft gamma-ray background and light dark matter annihilation

et al. 2006

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The bulk of the extragalactic background between 10 keV and 10 GeV is likely to be explained by the emission of Seyfert galaxies, type Ia supernovae, and blazars. However, as revealed by the INTEGRAL satellite, the bulge of our galaxy is an intense source of a 511 keV gamma-ray line, indicating the production of a large number of positrons that annihilate. The origin of the latter is debated, and they could be produced, in particular, by the (S-or P -wave) annihilation of light Dark Matter particles into e + e − . In any case, the cumulated effect of similar sources at all redshifts could lead to a new background of hard X-ray and soft gamma-ray photons. On the basis of the hierarchical model of galaxy formation, we compute analytically the SNIa contribution to the background, and add it to Seyfert and blazars emission models. Confronting these expected contributions to observation, we find that any extra contribution to this unresolved background around 511 keV should be lower than about 4 keV cm −2 s −1 sr −1 . We also estimate analytically the extragalactic background due to Dark Matter annihilation, increasing the accuracy of the earlier computations. Indeed, we take into account the large positron escape fraction from low mass dark matter halos, unable to confine a dense and magnetized interstellar medium. Our new background estimate turns out to be one order of magnitude lower so that the hypothesis of a light Dark Matter candidate remains compatible with the observed extragalactic background for a wider range of particle masses and cross-sections.PACS numbers: 95.35.+d, 95.85.Nv, 95.85.Pw, 97.60.Bw

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“…Direct detection experiments DAMA/LIBRA [1], COGENT [2], CRESST [3] have events consistent with a dark matter signal and there are several hints of indirect detection from the Fermi Gamma Ray Satellite and radio observations [4,5]. There are also two sets of observations of positrons that could be explained by dark matter: the observed excess of positrons over electrons in PAMELA [6] and INTEGRAL observations of the 511 keV line from the centre of the galaxy (see, e.g., [7][8][9] and [10] for a review).…”

mentioning

confidence: 99%

Cold positrons from decaying dark matter

2012

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Many models of dark matter contain more than one new particle beyond those in the Standard Model. Often heavier particles decay into the lightest dark matter particle as the Universe evolves. Here we explore the possibilities that arise if one of the products in a (Heavy Particle) → (Dark Matter) decay is a positron, and the lifetime is shorter than the age of the Universe. The positrons cool down by scattering off the cosmic microwave background and eventually annihilate when they fall into Galactic potential wells. The resulting 511 keV flux not only places constraints on this class of models but might even be consistent with that observed by the INTEGRAL satellite.

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Early SPI/INTEGRAL constraints on the morphology of the 511 keV line emission in the 4th galactic quadrant

Cited by 162 publications

References 19 publications

Gamma-ray continuum emission from the inner Galactic region as observed with INTEGRAL/SPI

Gamma-ray continuum emission from the inner Galactic region as observed with INTEGRAL/SPI

Soft gamma-ray background and light dark matter annihilation

Cold positrons from decaying dark matter

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