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No evidence for gamma-ray halos around active galactic nuclei resulting from intergalactic magnetic fields (Research Note)

par Neronov, Andrii;Semikoz, Dmitry D.V.;Tiniakov, Petr ;Tkachev, Igor
Référence Astronomy & astrophysics, 526, 11, A90
Publication Publié, 2011-02

Article révisé par les pairs

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Résumé :

We analyze the gamma-ray halo around stacked AGNs reported by Ando & Kusenko (2010, ApJ, 722, L39). First, we show that the angular distribution of γ-rays around the stacked AGNs is consistent with the angular distribution of the γ-rays around the Crab pulsar, which is a point source for Fermi/LAT. This makes it unlikely that the halo is caused by an electromagnetic cascade of TeV photons in the intergalactic space. We then compare the angular distribution of γ-rays around the stacked AGNs with the point-spread function (PSF) of Fermi/LAT and confirm the existence of an excess above the PSF. However, we demonstrate that the magnitude and the angular size of this effect is different for photons converted in the front and back parts of the Fermi/LAT instrument, and thus is an instrumental effect. © 2011 ESO.