Journal
ASTROPHYSICAL JOURNAL LETTERS
Volume 722, Issue 1, Pages L39-L44Publisher
IOP PUBLISHING LTD
DOI: 10.1088/2041-8205/722/1/L39
Keywords
galaxies: active; gamma rays: general; ISM: magnetic fields
Categories
Funding
- Japan Society for Promotion of Science
- NASA [NNX09AT74G, NNX08AL48G]
- DOE [DE-FG03-91ER40662]
- NASA [107645, NNX09AT74G] Funding Source: Federal RePORTER
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Intergalactic magnetic fields (IGMFs) 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 (AGNs) in the 11 month source catalog of the Fermi Gamma-Ray Space Telescope. Excess over the 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 AGNs. The halo size and brightness are consistent with IGMF, B-IGMF approximate to 10(-15) G. The knowledge of IGMF will facilitate the future gamma-ray and charged-particle astronomy. Furthermore, since IGMFs 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.
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