The Search for Spatial Extension in High-latitude Sources Detected by the Fermi Large Area Telescope

By M. Ackermann, M. Ajello, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, R. Bellazzini, E. Bissaldi, R. Blandford, E. Bloom and 102 more. Astrophysical Journal Supplement Series, 2018

154 citations recorded by the source corpus.

We present a search for spatial extension in high-latitude ( ) sources in recent Fermi point source catalogs. The result is the Fermi High-Latitude Extended Sources Catalog, which provides source extensions (or upper limits thereof) and likelihood profiles for a suite of tested source morphologies. We find 24 extended sources, 19 of which were not previously characterized as extended. These include sources that are potentially associated with supernova remnants and star-forming regions. We also found extended γ-ray emission in the vicinity of the Cen A radio lobes and—at GeV energies for the first time—spatially coincident with the radio emission of the SNR CTA 1, as well as from the Crab Nebula. We also searched for halos around active galactic nuclei, which are predicted from electromagnetic cascades induced by the e+e− pairs that are deflected in intergalactic magnetic fields. These pairs are produced when γ-rays interact with background radiation fields. We do not find evidence for extension in individual sources or in stacked source samples. This enables us to place limits on the flux of the extended source components, which are then used to constrain the intergalactic magnetic field to be stronger than 3 × 10−16 G for a coherence length λ ≳ 10 kpc, even when conservative assumptions on the source duty cycle are made. This improves previous limits by several orders of magnitude.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/e451c378af3d8d98b966c967013dbc7e51a848ea

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Citations in the corpus

A revised catalogue of 294 Galactic supernova remnants (2019, background): “Recently Ackermann et al. (2018) have shown extended γ-ray emission from much of G150.”
Fermi Large Area Telescope Fourth Source Catalog (2019, background): “The systematic search for extended sources outside the Galactic plane above 1GeV (FHES, Ackermann et al. 2018) found sixteen reliable extended sources.”