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Anisotropies in the diffuse gamma-ray background measured by the Fermi-LAT

Cuoco, A. and Linden, T. and Mazziotta, M. N. and Siegal-Gaskins, J. M. and Vitale, Vincenzo and Komatsu, E. (2012) Anisotropies in the diffuse gamma-ray background measured by the Fermi-LAT. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 692 . pp. 127-131. ISSN 0168-9002. https://resolver.caltech.edu/CaltechAUTHORS:20121204-082312053

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Abstract

The small angular scale fluctuations of the (on large scale) isotropic gamma-ray background (IGRB) carry information about the presence of unresolved source classes. A guaranteed contribution to the IGRB is expected from the unresolved gamma-ray AGN while other extragalactic sources, Galactic gamma-ray source populations and dark matter Galactic and extragalactic structures (and sub-structures) are candidate contributors. The IGRB was measured with unprecedented precision by the Large Area Telescope (LAT) on-board of the Fermi gamma-ray observatory, and these data were used for measuring the IGRB angular power spectrum (APS). Detailed Monte Carlo simulations of Fermi-LAT all-sky observations were performed to provide a reference against which to compare the results obtained for the real data set. The Monte Carlo simulations are also a method for performing those detailed studies of the APS contributions of single source populations, which are required in order to identify the actual IGRB contributors. We present preliminary results of an anisotropy search in the IGRB. At angular scales <2° (e.g., above multipole 155), angular power above the photon noise level is detected, at energies between 1 and 10 GeV in each energy bin, with statistical significance between 7.2 and 4.1σ. The obtained energy dependences point to the presence of one or more unclustered source populations with the components having an average photon index Γ=2.40±0.07.


Item Type:Article
Related URLs:
URLURL TypeDescription
http://dx.doi.org/10.1016/j.nima.2011.12.093DOIArticle
http://www.sciencedirect.com/science/article/pii/S0168900211023394PublisherArticle
http://arxiv.org/abs/1110.1047arXivDiscussion Paper
Additional Information:© 2012 Elsevier B.V. Available online 8 January 2012. The Fermi LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l'Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K.A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Études Spatiales in France.
Group:TAPIR
Funders:
Funding AgencyGrant Number
NASAUNSPECIFIED
Department of Energy (DOE)UNSPECIFIED
Commissariat à l’Energie AtomiqueUNSPECIFIED
Agenzia Spaziale Italiana (ASI)UNSPECIFIED
Ministry of Education, Culture, Sports, Science and Technology (MEXT)UNSPECIFIED
High Energy Accelerator Research Organization (KEK)UNSPECIFIED
Japan Aerospace Exploration Agency (JAXA)UNSPECIFIED
Knut and Alice Wallenberg FoundationUNSPECIFIED
Swedish Research CouncilUNSPECIFIED
Swedish National Space Board (SNSB) UNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Institut National de Physique Nucléaire et de Physique des Particules (IN2P3)UNSPECIFIED
Istituto Nazionale di Fisica Nucleare (INFN)UNSPECIFIED
Subject Keywords:γ rays; Dark matter; Isotropic γ - ray background; Extra-galactic γ - ray background
Record Number:CaltechAUTHORS:20121204-082312053
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20121204-082312053
Official Citation:A. Cuoco, T. Linden, M.N. Mazziotta, J.M. Siegal-Gaskins, Vincenzo Vitale, E. Komatsu, For the Fermi-LAT Collab, Anisotropies in the diffuse gamma-ray background measured by the Fermi-LAT, Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, Volume 692, 11 November 2012, Pages 127-131, ISSN 0168-9002, 10.1016/j.nima.2011.12.093. (http://www.sciencedirect.com/science/article/pii/S0168900211023394)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:35777
Collection:CaltechAUTHORS
Deposited By: Ruth Sustaita
Deposited On:04 Dec 2012 17:18
Last Modified:03 Oct 2019 04:31

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