Ackermann, M.M.AckermannAjello, M.M.AjelloBaldini, L.L.BaldiniCavazzuti, ElisabettaElisabettaCavazzutiCiprini, StefanoStefanoCipriniCutini, SaraSaraCutiniGasparrini, DarioDarioGasparrini2020-09-172020-09-172016-07-01https://hdl.handle.net/20.500.13025/4774The Astrophysical Journal, Volume 826, Issue 1, article id. 1, <NUMPAGES>9</NUMPAGES> pp. (2016).We report the Fermi Large Area Telescope detection of extended gamma-ray emission from the lobes of the radio galaxy Fornax A using 6.1 years of Pass 8 data. After Centaurus A, this is now the second example of an extended gamma-ray source attributed to a radio galaxy. Both an extended flat disk morphology and a morphology following the extended radio lobes were preferred over a point-source description, and the core contribution was constrained to be lt 14% of the total gamma-ray flux. A preferred alignment of the gamma-ray elongation with the radio lobes was demonstrated by rotating the radio lobes template. We found no significant evidence for variability on &tilde;0.5 year timescales. Taken together, these results strongly suggest a lobe origin for the gamma-rays. With the extended nature of the gt 100 {{MeV}} gamma-ray emission established, we model the source broadband emission considering currently available total lobe radio and millimeter flux measurements, as well as X-ray detections attributed to inverse Compton (IC) emission off the cosmic microwave background (CMB). Unlike the Centaurus A case, we find that a leptonic model involving IC scattering of CMB and extragalactic background light (EBL) photons underpredicts the gamma-ray fluxes by factors of about &tilde;2-3, depending on the EBL model adopted. An additional gamma-ray spectral component is thus required, and could be due to hadronic emission arising from proton-proton collisions of cosmic rays with thermal plasma within the radio lobes.galaxies activegalaxies individual Fornax Agalaxies jetsgamma rays galaxiesradiation mechanisms non-thermal10.3847/0004-637X/826/1/1http://adsabs.harvard.edu/abs/2016ApJ...826....1A2016ApJ...826....1A