Probing Intergalactic Magnetic Fields in the GLAST Era through Pair Echo Emission from TeV Blazars
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.
Keywords
Cite
@article{arxiv.0806.2829,
title = {Probing Intergalactic Magnetic Fields in the GLAST Era through Pair Echo Emission from TeV Blazars},
author = {Kohta Murase and Keitaro Takahashi and Susumu Inoue and Kiyomoto Ichiki and Shigehiro Nagataki},
journal= {arXiv preprint arXiv:0806.2829},
year = {2012}
}
Comments
4 pages, 3 figures, minor revisions, accepted for publication in APJL