Search for GeV γ -Ray Pair Halos Around Low Redshift Blazars

Wenlei Chen, James H. Buckley, Francesc Ferrer

Research output: Contribution to journalArticlepeer-review

62 Scopus citations


We report on the results of a search for γ-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 ∼1 GeV photons around 24 stacked isolated high-synchrotron-peaked BL Lacs with redshift z<0.5 shows an excess over that of pointlike sources. A frequentist test yields a p value of p∼0.01 for the extended emission against the point-source hypothesis. A Bayesian estimation provides Bayes factors log10B10>2, consistent with expectations for pair halos produced in the intergalactic magnetic fields with strength BIGMF∼10-17-10-15 G.

Original languageEnglish (US)
Article number211103
JournalPhysical review letters
Issue number21
StatePublished - Nov 16 2015

Fingerprint Dive into the research topics of 'Search for GeV γ -Ray Pair Halos Around Low Redshift Blazars'. Together they form a unique fingerprint.

Cite this