Fermi Large Area Telescope Gamma-Ray Detection of the Radio Galaxy M87

A. A. Abdo , Markus Ackermann , Marco Ajello , W. B. Atwood , Magnus Axelsson , Luca Baldini , Jean Ballet (1) , Guido Barbiellini , D. Bastieri , K. Bechtol , R. Bellazzini , B. Berenji , R. D. Blandford , E.D. Bloom , E. Bonamente , A.W. Borgland , J. Bregeon , A. Brez , M. Brigida , Pascal Bruel (2) , T.H. Burnett , G.A. Caliandro , R.A. Cameron , A. Cannon , P. A. Caraveo , J.M. Casandjian (1) , E. Cavazzuti , C. Cecchi , O. Celik , E. Charles , C.C. Cheung , J. Chiang , S. Ciprini , R. Claus , J. Cohen-Tanugi (3) , S. Colafrancesco , J. Conrad , L. Costamante , S. Cutini , D.S. Davis , C.D. Dermer , A. de Angelis , F. de Palma , S.W. Digel , D. Donato , E. Do Couto E Silva , P.S. Drell , R. Dubois , D. Dumora (4) , Y. Edmonds , C. Farnier (3) , C. Favuzzi , S.J. Fegan (2) , J. Finke , W.B. Focke , P. Fortin (2) , M. Frailis , Y. Fukazawa , S. Funk , P. Fusco , F. Gargano , D. Gasparrini , N. Gehrels , M. Georganopoulos , S. Germani , B. Giebels (2) , N. Giglietto , P. Giommi , F. Giordano , M. Giroletti , T. Glanzman , G. Godfrey , I.A. Grenier (1) , M.H. Grondin (4) , J.E. Grove , L. Guillemot (4) , S. Guiriec (3) , Y. Hanabata , A.K. Harding , M. Hayashida , E. Hays , D. Horan (2) , G. Jóhannesson , A.S. Johnson , R.P. Johnson , T.J. Johnson , W.N. Johnson , T. Kamae , H. Katagiri , J. Kataoka , N. Kawai , M. Kerr , Jürgen Knödlseder (5) , M. L. Kocian , M. Kuss , J. Lande , L. Latronico , M. Lemoine-Goumard (4) , F. Longo , F. Loparco , B. Lott (4) , M.N. Lovellette , P. Lubrano , G.M. Madjeski , A. Makeev , M.N. Mazziotta , W. Mcconville , J.E. Mcenery , C. Meurer , P.F. Michelson , W. Mitthumsiri , T. Mizuno , A.A. Moiseev , C. Monte , M.E. Monzani , A. Morselli , I.V. Moskalenko , S. Murgia , P.L. Nolan , J. P. Norris , E. Nuss (3) , T. Ohsugi , N. Omodei , E. Orlando , J.F. Ormes , M. Ozaki , D. Paneque , J.H. Panetta , D. Parent (4) , V. Pelassa (3) , M. Pepe , M. Pesce-Rollins , F. Piron (3) , T.A. Porter , S. Rainò , R. Rando , M. Razzano , A. Reimer , T. Reposeur (4) , S. Ritz , L.S. Rochester , A. Y. Rodriguez , R.W. Romani , F. Ryde , H. F.-W. Sadrozinski , R. Sambruna , D. Sanchez (2) , P.M. Saz Parkinson , J.D. Scargle , C. Sgrò , M. Shaw , D. A. Smith (4) , P. D. Smith , G. Spandre , P. Spinelli , M.S. Strickman , D.J. Suson , H. Tajima , H. Takahashi , T. Tanaka , G.B. Taylor , J.B. Thayer , D.J. Thompson , L. Tibaldo (1) , D.F. Torres , G. Tosti , A. Tramacere , Y. Uchiyama , T.L. Usher , V. Vasileiou , N. Vilchez (5) , A. P. Waite , P. Wang , B. L. Winer , K. S. Wood , T. Ylinen , M. Ziegler , D.E. Harris , F. Massaro , L. Stawarz

1 AIM (UMR7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
2 LLR - Laboratoire Leprince-Ringuet
3 LPTA - Laboratoire de Physique Théorique et Astroparticules
4 CENBG - Centre d'Etudes Nucléaires de Bordeaux Gradignan
5 CESR - Centre d'étude spatiale des rayonnements

We report the Fermi-LAT discovery of high-energy (MeV/GeV) gamma-ray emission positionally consistent with the center of the radio galaxy M87, at a source significance of over 10 sigma in ten-months of all-sky survey data. Following the detections of Cen A and Per A, this makes M87 the third radio galaxy seen with the LAT. The faint point-like gamma-ray source has a >100 MeV flux of 2.45 (+/- 0.63) x 10^-8 ph cm^-2 s^-1 (photon index = 2.26 +/- 0.13) with no significant variability detected within the LAT observation. This flux is comparable with the previous EGRET upper limit (< 2.18 x 10^-8 ph cm^-2 s^-1, 2 sigma), thus there is no evidence for a significant MeV/GeV flare on decade timescales. Contemporaneous Chandra and VLBA data indicate low activity in the unresolved X-ray and radio core relative to previous observations, suggesting M87 is in a quiescent overall level over the first year of Fermi-LAT observations. The LAT gamma-ray spectrum is modeled as synchrotron self-Compton (SSC) emission from the electron population producing the radio-to-X-ray emission in the core. The resultant SSC spectrum extrapolates smoothly from the LAT band to the historical-minimum TeV emission. Alternative models for the core and possible contributions from the kiloparsec-scale jet in M87 are considered, and can not be excluded.

Domaines: Phénomènes cosmiques de haute energie [astro-ph.HE]; Phénomènes cosmiques de haute energie [astro-ph.HE]

A. A. Abdo, Markus Ackermann, Marco Ajello, W. B. Atwood, Magnus Axelsson, et al.. Fermi Large Area Telescope Gamma-Ray Detection of the Radio Galaxy M87. The Astrophysical Journal, 2009, 707, pp.55-60. ⟨10.1088/0004-637X/707/1/55⟩. ⟨in2p3-00440769⟩