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
2013 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 765, no 1, 54- p.Article in journal (Refereed) Published
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.
galaxies: active, galaxies: halos, gamma rays: galaxies, instrumentation: detectors, intergalactic medium
IdentifiersURN: urn:nbn:se:kth:diva-119446DOI: 10.1088/0004-637X/765/1/54ISI: 000314957900054ScopusID: 2-s2.0-84874122100OAI: oai:DiVA.org:kth-119446DiVA: diva2:611658
FunderKnut and Alice Wallenberg Foundation
QC 201303182013-03-182013-03-142013-03-18Bibliographically approved