Determination of intergalactic magnetic fields from gamma ray data

We report a measurement of intergalactic magnetic fields using combined data from Atmospheric Cherenkov Telescopes and Fermi Gamma-Ray Space Telescope, based on the spectral data alone. If blazars are assumed to produce both gamma rays and cosmic rays, the observed spectra are not sensitive to the intrinsic spectrum of the source, because, for a distant blazar, secondary photons produced in line-of-sight cosmic-ray interactions dominate the signal. In this case, we find 0.01 fG < B < 30 fG. If one excludes the cosmic-ray component, the 0.01 fG lower limit remains, but the upper limit depends on the spectral properties of the source. We present the allowed ranges for a variety of model parameters.

💡 Research Summary

This research presents a method for measuring the intergalactic magnetic fields using interactions between gamma rays and cosmic rays. Data from Atmospheric Cherenkov Telescopes and the Fermi Gamma-Ray Space Telescope are combined to analyze these fields. When blazars, which are assumed to produce both gamma rays and cosmic rays, emit signals that travel over long distances, secondary photons produced by line-of-sight interactions between cosmic rays dominate the observed spectra. This means that the measured spectrum is less sensitive to the intrinsic properties of the source.

The study uses this interaction to estimate the range of intergalactic magnetic fields from 0.01 fG to 30 fG. If one excludes the cosmic-ray component, the lower limit remains at 0.01 fG, but the upper limit varies based on the spectral properties of the source. The researchers present allowed ranges for a variety of model parameters, which helps in refining the accuracy of intergalactic magnetic field measurements.

This method provides a novel approach to understanding the structure and strength of magnetic fields in intergalactic space by leveraging the interaction between gamma rays and cosmic rays emitted from distant blazars.