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DETERMINATION OF THE POINT-SPREAD FUNCTION FOR THE FERMI LARGE AREA TELESCOPE FROM ON-ORBIT DATA AND LIMITS ON PAIR HALOS OF ACTIVE GALACTIC NUCLEI
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2013 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 765, no 1, 54- p.Article in journal (Refereed) Published
Abstract [en]

The Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope is a pair-conversion telescope designed to detect photons with energies from approximate to 20 MeV to > 300 GeV. The pre-launch response functions of the LAT were determined through extensive Monte Carlo simulations and beam tests. The point-spread function (PSF) characterizing the angular distribution of reconstructed photons as a function of energy and geometry in the detector is determined here from two years of on-orbit data by examining the distributions of gamma rays from pulsars and active galactic nuclei (AGNs). Above 3 GeV, the PSF is found to be broader than the pre-launch PSF. We checked for dependence of the PSF on the class of gamma-ray source and observation epoch and found none. We also investigated several possible spatial models for pair-halo emission around BL Lac AGNs. We found no evidence for a component with spatial extension larger than the PSF and set upper limits on the amplitude of halo emission in stacked images of low-and high-redshift BL Lac AGNs and the TeV blazars 1ES0229 + 200 and 1ES0347-121.

Place, publisher, year, edition, pages
2013. Vol. 765, no 1, 54- p.
Keyword [en]
galaxies: active, galaxies: halos, gamma rays: galaxies, instrumentation: detectors, intergalactic medium
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
URN: urn:nbn:se:su:diva-88705DOI: 10.1088/0004-637X/765/1/54ISI: 000314957900054OAI: oai:DiVA.org:su-88705DiVA: diva2:612861
Funder
Knut and Alice Wallenberg Foundation
Note

AuthorCount:174;

Available from: 2013-03-25 Created: 2013-03-25 Last updated: 2017-12-06Bibliographically approved

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Conrad, JanLarsson, StefanYang, ZhaoyuZimmer, Stephan
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Department of PhysicsThe Oskar Klein Centre for Cosmo Particle Physics (OKC)Department of Astronomy
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