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

Ackermann M, Ajello M, Baldini L, Ballet J, Barbiellini G, Bastieri D, Bellazzini R, Bissaldi E, Blandford RD, Bloom ED, Bonino R, Bottacini E, Brandt TJ, Bregeon J, Bruel P, Buehler R, Cameron RA, Caputo R, Caraveo PA, Castro D, Cavazzuti E, Charles E, Cheung CC, Chiaro G, Ciprini S, Cohen-Tanugi J, Costantin D, Cutini S, D'Ammando F, De Palma F, Desai A, Di Lalla N, Di Mauro M, Di Venere L, Favuzzi C, Finke J, Franckowiak A, Fukazawa Y, Funk S, Fusco P, Gargano F, Gasparrini D, Giglietto N, Giordano F, Giroletti M, Green D, Grenier IA, Guillemot L, Guiriec S, Hays E, Hewitt JW, Horan D, Johannesson G, Kensei S, Kuss M, Larsson S, Latronico L, Lemoine-Goumard M, Li J, Longo F, Loparco F, Lovellette MN, Lubrano P, Magill JD, Maldera S, Manfreda A, Mazziotta MN, Mcenery JE, Meyer M, Mizuno T, Monzani ME, Morselli A, Moskalenko IV, Negro M, Nuss E, Omodei N, Orienti M, Orlando E, Ormes JF, Palatiello M, Paliya VS, Paneque D, Perkins JS, Persic M, Pesce-Rollins M, Piron F, Porter TA, Principe G, Raino S, Rando R, Rani B, Razzaque S, Reimer A, Reimer O, Reposeur T, Sgro C, Siskind EJ, Spandre G, Spinelli P, Suson DJ, Tajima H, Thayer JB, Tibaldo L, Torres DF, Tosti G, Valverde J, Venters TM, Vogel M, Wood K, Wood M, Zaharijas G, Biteau J (2018)

Publication Status: Published

Publication Type: Journal article

Publication year: 2018



Book Volume: 237

Article Number: ARTN 32

Journal Issue: 2

DOI: 10.3847/1538-4365/aacdf7


We present a search for spatial extension in high-latitude (vertical bar b vertical bar > 5 degrees) 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.-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 gamma-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 x 10(-16) G for a coherence length lambda greater than or similar to 10 kpc, even when conservative assumptions on the source duty cycle are made. This improves previous limits by several orders of magnitude.

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Involved external institutions

National Institute for Nuclear Physics / Istituto Nazionale di Fisica Nucleare (INFN) IT Italy (IT) University of Paris 7 - Denis Diderot / Université Paris VII Denis Diderot FR France (FR) National Aeronautics and Space Administration (NASA) US United States (USA) (US) U.S. Naval Research Laboratory US United States (USA) (US) University of Montpellier / Université Montpellier FR France (FR) University of Maryland US United States (USA) (US) Stanford University US United States (USA) (US) Institute of Space Sciences (IEEC-CSIC) ES Spain (ES) Royal Institute of Technology / Kungliga Tekniska Högskolan (KTH) SE Sweden (SE) University of Iceland (UI) / Háskóli Íslands IS Iceland (IS) École Polytechnique - Université Paris-Saclay FR France (FR) National Institute for Astrophysics / Istituto Nazionale Astrofisica (INAF) IT Italy (IT) University of Bari Aldo Moro / Università degli Studi di Bari Aldo Moro IT Italy (IT) Italian Space Agency / Agenzia Spaziale Italiana (ASI) IT Italy (IT) Hiroshima University / 広島大学 JP Japan (JP) Deutsches Elektronen-Synchrotron DESY DE Germany (DE) University of Pisa / Università di Pisa (UniPi) IT Italy (IT) Clemson University US United States (USA) (US) Université Bordeaux 1, Sciences et Technologies FR France (FR) California State University, Los Angeles US United States (USA) (US) University of Paris 11 - Paris-Sud / Université Paris XI Paris-Sud FR France (FR) National Center for Scientific Research / Centre national de la recherche scientifique (CNRS) FR France (FR) Purdue University Northwest / Purdue University Calumet US United States (USA) (US) NYCB Real-Time Computing, Inc. US United States (USA) (US) University of Johannesburg ZA South Africa (ZA) Praxis, Inc. US United States (USA) (US) Max-Planck-Institut für Physik (Werner-Heisenberg-Institut, MPP) / Max Planck Institute for Physics DE Germany (DE) University of Denver US United States (USA) (US) University of Padua / Universita degli Studi di Padova IT Italy (IT) University of North Florida (UNF) US United States (USA) (US) University of Orléans / Université d'Orléans FR France (FR)

How to cite


Ackermann, M., Ajello, M., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D.,... Biteau, J. (2018). The Search for Spatial Extension in High-latitude Sources Detected by the Fermi Large Area Telescope. Astrophysical Journal Supplement Series, 237(2).


Ackermann, Markus, et al. "The Search for Spatial Extension in High-latitude Sources Detected by the Fermi Large Area Telescope." Astrophysical Journal Supplement Series 237.2 (2018).

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