Constraining the intergalactic magnetic field by means of gamma ray observation

During the last decade, for the first time, a method to constrain the intergalactic magnetic field (IGMF) using gamma ray observations was successfully applied. High energy gamma rays initiate electromagnetic cascades on the infrared background which are sensitive to the configuration of the IGMF. The produced secondary gamma rays can then be used to constrain the IGMF. Recently, among others, both the MAGIC and HESS collaborations presented catalogs of newly discovered very high energy sources (VHE, E>100 GeV) which can be used for this purpose. In this work, we use two of these sources, 2WHSP J073326.7+515354 and MRC 0910-208, to find a lower boundary for the strength of the intergalactic magnetic field. Other than in the original work, we use the published SED source models to infer the intrinsic very high energy spectra. This allowed us to predict the amount of cascade emission in the GeV domain for different IGMF settings. From the analysis of the aforementioned sources with a fixed IGMF correlation length, we can infer the lower limit for the strength of the IGMF to be 6 · 10 −17 G. (author)