Constraints on the Intergalactic Magnetic Field from Bow Ties in the Gamma-ray Sky

Abstract

Pair creation on the cosmic infrared background and subsequent inverse-Compton scattering on the CMB potentially reprocesses the TeV emission of blazars into faint GeV halos with structures sensitive to intergalactic magnetic fields (IGMF). Previous work has shown that these halos are then highly-anisotropic and extended. If the coherence length of the IGMF is greater than the inverse-Compton cooling length of the pairs, then the orientation of the gamma-ray halo will be correlated with the direction of the magnetic field which is unknown and expected to change for each source. In order to constructively add each source we then use angular power spectra which are insensitive to the jet orientation. By looking at known GeV blazars detected by Fermi, we exclude the existence of an IGMF with coherence lengths $>100$ Mpc at greater than $3.9\sigma$ with current-day strengths in the range $10^{-16}$ to $10^{-15}$ G, and at 2$\sigma$ from $10^{-17}$ to $10^{-14}$ G. This provides a direct measurement of the non-existence of gamma-ray halos, providing an important check on previous results.

12 pages, 14 figures, 1 appendix. Accepted to ApJ

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Cited by in corpus (10)

• The Gamma-Ray Window to Intergalactic Magnetism
• Seed magnetic fields in turbulent small-scale dynamos
• Suppression of the TeV pair-beam plasma instability by a tangled weak intergalactic magnetic field
• Modelling the propagation of very-high-energy gamma rays with the CRbeam code: Comparison with CRPropa and ELMAG codes
• Revisiting primordial magnetic fields through 21-cm physics: Bounds and forecasts
• Constraining blazar heating with the 2<z<3 Lyman-$\alpha$ forest
• Energy Dissipation in Strong Collisionless Shocks: The Crucial Role of Ion-to-Electron Scale Separation in Particle-in-Cell Simulations
• The Impact of Inhomogeneous Perturbations of the Inflaton on the Cosmological Primordial Magnetic Field
• Primordial magnetic non-Gaussianity with generic vacua and detection prospects in CMB spectral distortions
• Sensitivity of the redshifted 21 cm signal from the Dark Ages to parameters of primordial magnetic fields