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Bow Ties in the Sky. II. Searching for Gamma-Ray Halos in the Fermi Sky Using Anisotropy

Tiede, Paul and Broderick, Avery E. and Shalaby, Mohamad and Pfrommer, Christoph and Puchwein, Ewald and Chang, Philip and Lamberts, Astrid (2017) Bow Ties in the Sky. II. Searching for Gamma-Ray Halos in the Fermi Sky Using Anisotropy. Astrophysical Journal, 850 (2). Art. No. 157. ISSN 1538-4357.

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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 relativistic electron/positron pairs generated by the annihilation of ≳100 GeV gamma rays on the extragalactic background light. These are typically anisotropic due to the jetted structure from which they originate (in the case of radio galaxies) or are oriented perpendicular to a large-scale intergalactic magnetic field (for blazar geometries). Here, we propose a novel method for detecting these inverse Compton gamma-ray halos based on this anisotropic structure that is centered on the active galactic nucleus (AGN). By marginalizing over the radial distribution of halo photons, we demonstrate that the angular power spectrum shows a characteristic sawtooth pattern with a dominant dipolar power and elevated even multipoles. Specifically, we show that by stacking those angular power spectra instead of images, it is possible to robustly detect gamma-ray halos with existing Fermi Large Area Telescope (LAT) observations for a broad class of intergalactic magnetic fields. Importantly, by testing a large number of systematics, our suggested power spectrum statistics appears to be robust and unbiased with respect to systematic uncertainties within the LAT instrumental response and associated with contaminating astronomical sources.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Tiede, Paul0000-0003-3826-5648
Broderick, Avery E.0000-0002-3351-760X
Shalaby, Mohamad0000-0001-9625-5929
Pfrommer, Christoph0000-0002-7275-3998
Chang, Philip0000-0002-2137-2837
Lamberts, Astrid0000-0001-8740-0127
Additional Information:© 2017 The American Astronomical Society. Received 2016 September 15; revised 2017 September 28; accepted 2017 October 8; published 2017 November 28. A.E.B. and M.S. receive financial support from the Perimeter Institute for Theoretical Physics and the Natural Sciences and Engineering Research Council of Canada through a Discovery Grant. Research at the Perimeter Institute is supported by the Government of Canada through Industry Canada and by the Province of Ontario through the Ministry of Research and Innovation. C.P. acknowledges support by the European Research Council under ERC-CoG grant CRAGSMAN-646955 and by the Klaus Tschira Foundation. P.C. gratefully acknowledges support from the NASA ATP program through NASA grant NNX13AH43G, and NSF grant AST-1255469. A.L. receives financial support from an Alfred P. Sloan Research Fellowship, NASA ATP Grant NNX14AH35G, and NSF Collaborative Research Grant 411920 and CAREER grant 1455342. E.P. acknowledges support by the Kavli Foundation.
Funding AgencyGrant Number
Perimeter Institute for Theoretical PhysicsUNSPECIFIED
Natural Sciences and Engineering Research Council of Canada (NSERC)UNSPECIFIED
Industry CanadaUNSPECIFIED
Ontario Ministry of Research and InnovationUNSPECIFIED
European Research Council (ERC)CRAGSMAN-646955
Klaus Tschira FoundationUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Kavli FoundationUNSPECIFIED
Subject Keywords:BL Lacertae objects: general – gamma rays: diffuse background – gamma rays: general – infrared: diffuse background – plasmas – radiation mechanisms: non-thermal
Issue or Number:2
Record Number:CaltechAUTHORS:20171128-145723001
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83550
Deposited By: Tony Diaz
Deposited On:28 Nov 2017 23:09
Last Modified:09 Mar 2020 13:19

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