THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV

Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, Luca; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Brandt, T. J.; Bregeon, J.; Bruel, Pascal; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cuoco, A.; Cutini, S.; D’Ammando, F.; Angelis, A. De; Palma, F. de; Dermer, C. D.; Digel, S. W.; Silva, E. do Couto e; Drell, P. S.; Favuzzi, C.; Ferrara, E. C.; Focke, W. B.; Franckowiak, A.; Fukazawa, Yasushi; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Godfrey, G.; Gomez-Vargas, G. A.; Grenier, I. A.; Guiriec, S.; Gustafsson, M.; Hadasch, D.; Hayashi, K.; Hays, E.; Hewitt, John W.; Ippoliti, P.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kamae, T.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Larsson, Stefan; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Manfreda, Alberto; Massaro, F.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Моисеев, А. А.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nemmen, R.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Panetta, J.; Perkins, J. S.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Reposeur, T.; Ritz, S.; Romani, Roger W.; Sánchez‐Conde, Miguel A.; Schaal, M.; Schulz, A.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Strong, A. W.; Suson, D. J.; Takahashi, H.; Thayer, J. G.; Thayer, J. B.; Tibaldo, L.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Vianello, G.; Werner, M. W.; Winer, B. L.; Wood, K. S.; Wood, M.; Zaharijaš, Gabrijela; Zimmer, S.

doi:10.1088/0004-637x/799/1/86

Cited by 753 publications

(1,059 citation statements)

References 99 publications

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“…Next, we compute the secondary neutrino and photon fluxes. We compare them respectively to the astrophysical neutrino flux (magenta errorbars) measured by IceCube [17] and to the measurement (red errorbars) of the extragalactic γ-ray background (EGB) by Fermi-LAT [16]. For the latter, we show both the IGRB (lower curve) and the total EGB including resolved sources (upper curve).…”

Section: B Diffuse Fluxes From Normal Spiral and Starburst Galaxiesmentioning

confidence: 99%

“…In this work, we investigate which CR source classes can explain the extragalactic proton component derived within the escape model [14,15] and, at the same time, can give a significant contribution to the isotropic γ-ray background (IGRB) measured by Fermi-LAT [16] and to the astrophysical neutrino signal observed by IceCube [17]. These neutrinos have been suggested to have either a Galactic (e.g.…”

Section: Both Light and Intermediate Elements Above This Energymentioning

confidence: 99%

“…Diffuse CR proton (blue), gamma-ray (red) and neutrino (magenta) fluxes from starburst galaxies together with CR proton data from KASCADE, KASCADE-Grande [5] and Auger (black errorbars) [4,52], the IGRB and the EGB from Fermi-LAT (red errorbars) [16], and high-energy neutrino flux from IceCube (magenta errorbars) [17]. Solid red and magenta lines for gamma-ray and neutrino fluxes with n = 1 cm −3 , and dashed lines for n = 10 cm −3 .…”

Section: Figmentioning

confidence: 99%

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Unified model for cosmic rays above1017 eVand the diffuse gamma-ray and neutrino backgrounds

et al. 2015

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We investigate how the extragalactic proton component derived within the "escape model" can be explained by astrophysical sources. We consider as possible cosmic ray (CR) sources normal/starburst galaxies and radio-loud active galactic nuclei (AGN). We find that the contribution to the total extragalactic proton flux from normal and starburst galaxies is only subdominant and does not fit the spectral shape deduced in the escape model. In the case of radio-loud AGN, we show that the complete extragalactic proton spectrum can be explained by a single source population, BL Lac/FR I, for any of the potential acceleration sites in these sources. We calculate the diffuse neutrino and γ-ray fluxes produced by these CR protons interacting with gas inside their sources. For a spectral slope of CRs close to α = 2.1 − 2.2 as suggested by shock acceleration, we find that these UHECR sources contribute the dominant fraction of both the isotropic γ-ray background and of the extragalactic part of the astrophysical neutrino signal observed by IceCube.

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Section: B Diffuse Fluxes From Normal Spiral and Starburst Galaxiesmentioning

confidence: 99%

Section: Both Light and Intermediate Elements Above This Energymentioning

confidence: 99%

Section: Figmentioning

confidence: 99%

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Unified model for cosmic rays above1017 eVand the diffuse gamma-ray and neutrino backgrounds

et al. 2015

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“…An isotropic background, which accounts for an approximately isotropic diffuse γ-ray emission component and residual CRs misclassified as γ-rays in the LAT. The origin of the astrophysical emission is currently unclear and it may come from multiple sources, ranging from the solar system to cosmological structures (Ackermann et al 2015a). It was modelled using the publicly available isotropic spectral model iso_source_v05.txt, with free normalisation in the fit.…”

Section: Background Modelmentioning

confidence: 99%

Deep view of the Large Magellanic Cloud with six years ofFermi-LAT observations

Ackermann¹,

Albert²,

Atwood³

et al. 2016

A&A

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Context. The nearby Large Magellanic Cloud (LMC) provides a rare opportunity of a spatially resolved view of an external star-forming galaxy in γ-rays. The LMC was detected at 0.1-100 GeV as an extended source with CGRO/EGRET and using early observations with the Fermi-LAT. The emission was found to correlate with massive star-forming regions and to be particularly bright towards 30 Doradus. Aims. Studies of the origin and transport of cosmic rays (CRs) in the Milky Way are frequently hampered by line-of-sight confusion and poor distance determination. The LMC offers a complementary way to address these questions by revealing whether and how the γ-ray emission is connected to specific objects, populations of objects, and structures in the galaxy. Methods. We revisited the γ-ray emission from the LMC using about 73 months of Fermi-LAT P7REP data in the 0.2-100 GeV range. We developed a complete spatial and spectral model of the LMC emission, for which we tested several approaches: a simple geometrical description, template-fitting, and a physically driven model for CR-induced interstellar emission. Results. In addition to identifying PSR J0540−6919 through its pulsations, we find two hard sources positionally coincident with plerion N 157B and supernova remnant N 132D, which were also detected at TeV energies with H.E.S.S. We detect an additional soft source that is currently unidentified. Extended emission dominates the total flux from the LMC. It consists of an extended component of about the size of the galaxy and additional emission from three to four regions with degree-scale sizes. If it is interpreted as CRs interacting with interstellar gas, the large-scale emission implies a large-scale population of ∼1-100 GeV CRs with a density of ∼30% of the local Galactic value. On top of that, the three to four small-scale emission regions would correspond to enhancements of the CR density by factors 2 to 6 or higher, possibly more energetic and younger populations of CRs compared to the large-scale population. An alternative explanation is that this is emission from an unresolved population of at least two dozen objects, such as pulsars and their nebulae or supernova remnants. This small-scale extended emission has a spatial distribution that does not clearly correlate with known components of the LMC, except for a possible relation to cavities and supergiant shells. Conclusions. The Fermi-LAT GeV observations allowed us to detect individual sources in the LMC. Three of the newly discovered sources are associated with rare and extreme objects. The 30 Doradus region is prominent in GeV γ-rays because PSR J0540−6919 and N 157B are strong emitters. The extended emission from the galaxy has an unexpected spatial distribution, and observations at higher energies and in radio may help to clarify its origin.

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“…2 Assuming that the halos are isotropically distributed across the Universe, the number of halos at redshift z is proportional to the comoving volume δV (z) of the corresponding redshift slice δz, therefore we also have P (z) = dN/dz ∝ dV /dz. Alternatively, we can rewrite Eq.…”

Section: Pdf For the Flux From Individual Halosmentioning

confidence: 99%

Modelling the flux distribution function of the extragalactic gamma-ray background from dark matter annihilation

Feyereisen

Ando

Lee

2015

J. Cosmol. Astropart. Phys.

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Abstract. The one-point function (i.e., the isotropic flux distribution) is a complementary method to (anisotropic) two-point correlations in searches for a gamma-ray dark matter annihilation signature. Using analytical models of structure formation and dark matter halo properties, we compute the gamma-ray flux distribution due to annihilations in extragalactic dark matter halos, as it would be observed by the Fermi Large Area Telescope. Combining the central limit theorem and Monte Carlo sampling, we show that the flux distribution takes the form of a narrow Gaussian of 'diffuse' light, with an 'unresolved point source' power-law tail as a result of bright halos. We argue that this background due to dark matter constitutes an irreducible and significant background component for point-source annihilation searches with galaxy clusters and dwarf spheroidal galaxies, modifying the predicted signal-to-noise ratio. A study of astrophysical backgrounds to this signal reveals that the shape of the total gamma-ray flux distribution is very sensitive to the contribution of a dark matter component, allowing us to forecast promising one-point upper limits on the annihilation cross section. We show that by using the flux distribution at only one energy bin, one can probe the canonical cross section required for explaining the relic density, for dark matter of masses around tens of GeV.

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THE SPECTRUM OF ISOTROPIC DIFFUSE GAMMA-RAY EMISSION BETWEEN 100 MeV AND 820 GeV

Cited by 753 publications

References 99 publications

Unified model for cosmic rays above1017 eVand the diffuse gamma-ray and neutrino backgrounds

Unified model for cosmic rays above1017 eVand the diffuse gamma-ray and neutrino backgrounds

Deep view of the Large Magellanic Cloud with six years ofFermi-LAT observations

Modelling the flux distribution function of the extragalactic gamma-ray background from dark matter annihilation

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