Abstract
We report on the results of a search for -ray pair halos with a stacking analysis of low redshift blazars using data from the Fermi Large Area Telescope. For this analysis we used a number of a priori selection criteria, including the spatial and spectral properties of the Fermi sources. The angular distribution of photons around 24 stacked isolated high-synchrotron-peaked BL Lacs with redshift shows an excess over that of pointlike sources. A frequentist test yields a value of for the extended emission against the point-source hypothesis. A Bayesian estimation provides Bayes factors , consistent with expectations for pair halos produced in the intergalactic magnetic fields with strength .
- Received 28 October 2014
DOI:https://doi.org/10.1103/PhysRevLett.115.211103
© 2015 American Physical Society