Astrophysics > High Energy Astrophysical Phenomena
[Submitted on 11 May 2010 (v1), last revised 2 Sep 2010 (this version, v2)]
Title:Evidence for Gamma-Ray Halos Around Active Galactic Nuclei and the First Measurement of Intergalactic Magnetic Fields
View PDFAbstract:Intergalactic magnetic fields (IGMF) can cause the appearance of halos around the gamma-ray images of distant objects because an electromagnetic cascade initiated by a high-energy gamma-ray interaction with the photon background is broadened by magnetic deflections. We report evidence of such gamma-ray halos in the stacked images of the 170 brightest active galactic nuclei (AGN) in the 11-month source catalog of the Fermi Gamma-Ray Space Telescope. Excess over point spread function in the surface brightness profile is statistically significant at 3.5\sigma (99.95% confidence level), for the nearby, hard population of AGN. The halo size and brightness are consistent with IGMF, B_{IGMF} ~ 10^{-15} G. The knowledge of IGMF will facilitate the future gamma-ray and charged-particle astronomy. Furthermore, since IGMF are likely to originate from the primordial seed fields created shortly after the Big Bang, this potentially opens a new window on the origin of cosmological magnetic fields, inflation, and the phase transitions in the early Universe.
Submission history
From: Shin'ichiro Ando [view email][v1] Tue, 11 May 2010 19:59:59 UTC (116 KB)
[v2] Thu, 2 Sep 2010 19:57:16 UTC (122 KB)
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