Evidence for Gamma-ray Halos Around Active Galactic Nuclei and the First Measurement of Intergalactic Magnetic Fields

@article{Ando2010EvidenceFG,
title={Evidence for Gamma-ray Halos Around Active Galactic Nuclei and the First Measurement of Intergalactic Magnetic Fields},
author={S. Ando and A. Kusenko},
journal={The Astrophysical Journal},
year={2010},
volume={722}
}
• Published 2010
• Physics
• The Astrophysical Journal
Intergalactic magnetic fields (IGMFs) can cause the appearance of halos around the gamma-ray images of distant objects because an electromagnetic cascade initiated by a high-energy gamma-ray interaction with the photon background is broadened by magnetic deflections. We report evidence of such gamma-ray halos in the stacked images of the 170 brightest active galactic nuclei (AGNs) in the 11 month source catalog of the Fermi Gamma-Ray Space Telescope. Excess over the point-spread function in the… Expand
132 Citations

Figures from this paper

No evidence for gamma-ray halos around active galactic nuclei resulting from intergalactic magnetic fields
• Physics
• 2010
We analyze the gamma-ray halo around stacked AGNs reported in Ap.J.Lett., 2010, 722, L39. First, we show that the angular distribution of gamma-rays around the stacked AGNs is consistent with theExpand
Missing Gamma-ray Halos and the Need for New Physics in the Gamma-ray Sky
An intergalactic magnetic field stronger than $3\times10^{-13}$~G would explain the lack of a bright, extended degree-scale, GeV-energy inverse Compton component in the gamma-ray spectra ofExpand
Prospect on intergalactic magnetic field measurements with gamma-ray instruments
Abstract Observing high-energy gamma-rays from Active Galactic Nuclei (AGN) offers a unique potential to probe extremely tiny values of the intergalactic magnetic field (IGMF), a long standingExpand
Bow Ties in the Sky. II. Searching for Gamma-Ray Halos in the Fermi Sky Using Anisotropy
Many-degree-scale gamma-ray halos are expected to surround extragalactic high-energy gamma-ray sources. These arise from the inverse Compton emission of an intergalactic population of relativisticExpand
Probing the Intergalactic Magnetic Field with the Anisotropy of the Extragalactic Gamma-Ray Background
• Physics
• 2013
ABSTRACT The intergalactic magnetic field (IG:YIF) may leave an imprint on the anisotropy prop­erties of the extragalactic gamma-ray background, through its effect on electromag­netic cascadesExpand
Bow Ties in the Sky I: The Angular Structure of Inverse Compton Gamma-ray Halos in the Fermi Sky
Extended inverse Compton halos are generally anticipated around extragalactic sources of gamma rays with energies above 100 GeV. These result from inverse Compton scattered cosmic microwaveExpand
Constraints on the Intergalactic Magnetic Field from Bow Ties in the Gamma-Ray Sky
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 sensitiveExpand
Probing early cosmic magnetic fields through pair echoes from high‐redshift GRBs
• Physics
• 2010
We discuss the expected properties of pair echo emission from gamma-ray bursts (GRBs) at high redshifts (z ≳ 5), their detectability, and the consequent implications for probing intergalacticExpand
Role of Line-of-sight Cosmic-ray Interactions in Forming the Spectra of Distant Blazars in TeV Gamma Rays and High-energy Neutrinos
• Physics
• 2011
Active galactic nuclei (AGNs) can produce both gamma rays and cosmic rays. The observed high-energy gamma-ray signals from distant blazars may be dominated by secondary gamma rays produced along theExpand
Detectability of ultrahigh energy cosmic-ray signatures in gamma-rays
• Physics
• 2011
The injection of ultrahigh energy cosmic-rays in the intergalactic medium leads to the production of a GeV–TeV gamma-ray halo centered on the source location, through the production of a highExpand

References

SHOWING 1-10 OF 31 REFERENCES
A comment on "Discovery of gamma-ray halos around active galactic nuclei and the first measurement of intergalactic magnetic fields"
• Physics
• 2010
We analyze the gamma-ray halo around stacked AGNs reported in arXiv:1005.1924. First, we show that the angular distribution of gamma-rays of 10-100 GeV around the stacked AGNs is consistent with theExpand
A new interpretation of the gamma-ray observations of distant active galactic nuclei
• Physics
• 2010
Abstract Gamma-ray telescopes have reported some surprising observations of multi-TeV photons from distant active galactic nuclei (AGN), which show no significant attenuation due to pair productionExpand
Search for a TeV gamma-ray halo of Mkn 501
• Physics
• 2000
For distant extragalactic sources of gamma-rays in the PeV (10 15 eV) energy range, interactions of the gamma rays with intergalactic diuse radiation elds will initiate a pair cascade. Depending onExpand
Sensitivity of {gamma}-ray telescopes for detection of magnetic fields in the intergalactic medium
• Physics
• 2009
We explore potential of current and next-generation {gamma}-ray telescopes for the detection of weak magnetic fields in the intergalactic medium. We demonstrate that using two complementaryExpand
Fermi large area telescope measurements of the diffuse gamma-ray emission at intermediate galactic latitudes.
The Large Area Telescope (LAT) instrument on the Fermi Gamma-Ray Space Telescope has measured the diffuse gamma-ray emission with improved sensitivity and resolution compared to EGRET, and the LAT spectrum for this region of the sky is well reproduced by a diffuse galactic gamma-rays emission model that is consistent with local CR spectra and inconsistent with the EGRET GeV excess. Expand
Probing Intergalactic Magnetic Fields in the GLAST Era through Pair Echo Emission from TeV Blazars
• Physics
• 2008
More than a dozen blazars are known to be emitters of multi-TeV gamma rays, often with strong and rapid flaring activity. By interacting with photons of the cosmic microwave and infrared backgrounds,Expand
Spectrum of the isotropic diffuse gamma-ray emission derived from first-year Fermi Large Area Telescope data.
The first Fermi Large Area Telescope measurements of the so-called "extragalactic" diffuse gamma-ray emission (EGB) are reported, finding the spectrum is featureless, less intense, and softer than that derived from EGRET data. Expand
Search for an extended VHE gamma-ray emission from Mrk 421 and Mrk 501 with the MAGIC Telescope
Context. Part of the very high energy -ray radiation coming from extragalactic sources is absorbed through the pair production process on the extragalactic background light photons. Extragalacti cExpand
Evidence for Strong Extragalactic Magnetic Fields from Fermi Observations of TeV Blazars
• Physics, Medicine
• Science
• 2010
A lower bound B ≥ 3 × 10−16 gauss on the strength of intergalactic magnetic fields is reported, which stems from the nonobservation of GeV gamma-ray emission from electromagnetic cascade initiated by tera–electron volt gamma rays inintergalactic medium. Expand
Detecting intergalactic magnetic fields using time delays in pulses of γ-rays
INTERGALACTIC magnetic fields (IGMFs) can be produced by a number of mechanisms, but are expected to be weak and have not so far been detected. 'Primordial' magnetic fields might have been producedExpand