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arXiv · 0806.2829

Probing Intergalactic Magnetic Fields in the GLAST Era through Pair Echo Emission from TeV Blazars

Kohta Murase·Keitaro Takahashi·Susumu Inoue·Kiyomoto Ichiki·Shigehiro Nagataki
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Abstract

More than a dozen blazars are known to be emitters of multi-TeV gamma rays, often with strong and rapid flaring activity. By interacting with photons of the cosmic microwave and infrared backgrounds, these gamma rays inevitably produce electron-positron pairs, which in turn radiate secondary inverse Compton gamma rays in the GeV-TeV range with a characteristic time delay that depends on the properties of the intergalactic magnetic field (IGMF). For sufficiently weak IGMF, such "pair echo" emission may be detectable by the Gamma-ray Large Area Space Telescope (GLAST), providing valuable information on the IGMF. We perform detailed calculations of the time-dependent spectra of pair echos from flaring TeV blazars such as Mrk 501 and PKS 2155-304, taking proper account of the echo geometry and other crucial effects. In some cases, the presence of a weak but non-zero IGMF may enhance the detectability of echos. We discuss the quantitative constraints that can be imposed on the IGMF from GLAST observations, including the case of non-detections.

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Kohta Murase, Keitaro Takahashi, Susumu Inoue, Kiyomoto Ichiki, Shigehiro Nagataki. 2008-06-17. Probing Intergalactic Magnetic Fields in the GLAST Era through Pair Echo Emission from TeV Blazars. https://doi.org/10.1086/592997

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