Observations of the Large Magellanic Cloud with Fermi

A.A. Abdo , Markus Ackermann , Marco Ajello , W. B. Atwood , Luca Baldini , Jean Ballet (1) , Guido Barbiellini , D. Bastieri , B. M. Baughman , K. Bechtol , R. Bellazzini (1) , B. Berenji , R. D. Blandford , E. D. Bloom , E. Bonamente , A. W. Borgland , J. Bregeon (2) , A. Brez , M. Brigida , Pascal Bruel (3) , T. H. Burnett , S. Buson , G. A. Caliandro , R. A. Cameron , P. A. Caraveo , J. M. Casandjian (1) , C. Cecchi , Ö. Çelik , A. Chekhtman , C. C. Cheung , J. Chiang , S. Ciprini , R. Claus , J. Cohen-Tanugi , L. R. Cominsky , J. Conrad , S. Cutini , C. D. Dermer , A. de Angelis , F. de Palma , S. W. Digel , E. Do Couto E Silva , P. S. Drell , R. Dubois , D. Dumora (2) , C. Farnier , C. Favuzzi , S. J. Fegan (3) , W. B. Focke , P. Fortin (3) , M. Frailis , Y. Fukazawa , P. Fusco , F. Gargano , D. Gasparrini , N. Gehrels , S. Germani , G. Giavitto , B. Giebels (3) , N. Giglietto , F. Giordano , T. Glanzman , G. Godfrey , E. V. Gotthelf , I. A. Grenier (1) , M.-H. Grondin (2) , J. E. Grove , L. Guillemot (2) , S. Guiriec , Y. Hanabata , A. K. Harding , M. Hayashida , E. Hays , D. Horan (3) , R. E. Hughes , M. S. Jackson , P. Jean , 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 (4) , M. L. Kocian , M. Kuss , J. Lande , L. Latronico , M. Lemoine-Goumard (2) , F. Longo , F. Loparco , B. Lott (2) , M. N. Lovellette , P. Lubrano , G. M. Madejski , A. Makeev , F. Marshall , P. Martin , 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 , T. Ohsugi , N. Omodei , E. Orlando , J. F. Ormes , D. Paneque , D. Parent (2) , V. Pelassa , M. Pepe , M. Pesce-Rollins , F. Piron , T.A. Porter , S. Rainò , R. Rando , M. Razzano , A. Reimer , O. Reimer , T. Reposeur (2) , S. Ritz , A. Y. Rodriguez , R. W. Romani , M. Roth , F. Ryde , H. F.-W. Sadrozinski , D. Sanchez (3) , A. Sander , P. M. Saz Parkinson , J. D. Scargle (1) , A. Sellerholm , C. Sgrò (3) , E. J. Siskind , David Stanley Smith (2) , P. D. Smith , G. Spandre , P. Spinelli , Jean-Luc Starck (1) , M. S. Strickman , A. W. Strong , D. J. Suson , H. Tajima , H. Takahashi , T. Tanaka , J. B. Thayer , J. G. Thayer , D. J. Thompson , L. Tibaldo (1) , D. F. Torres , G. Tosti , A. Tramacere , Y. Uchiyama , T. L. Usher , V. Vasileiou , C. Venter , N. Vilchez (4) , V. Vitale , A. P. Waite , P. Wang , P. Weltevrede , B. L. Winer , K. S. Wood , T. Ylinen , M. Ziegler

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

Context: The Large Magellanic Cloud (LMC) is to date the only normal external galaxy that has been detected in high-energy gamma rays. High-energy gamma rays trace particle acceleration processes and gamma-ray observations allow the nature and sites of acceleration to be studied. Aims: We characterise the distribution and sources of cosmic rays in the LMC from analysis of gamma-ray observations. Methods: We analyse 11 months of continuous sky-survey observations obtained with the Large Area Telescope aboard the Fermi Gamma-Ray Space Telescope and compare it to tracers of the interstellar medium and models of the gamma-ray sources in the LMC. Results: The LMC is detected at 33 sigma significance. The integrated >100 MeV photon flux of the LMC amounts to (2.6 +/- 0.2) * 10^-7 ph/cm2/s which corresponds to an energy flux of (1.6 +/- 0.1) * 10^-10 erg/cm2/s, with additional systematic uncertainties of ~16%. The analysis reveals the massive star forming region 30 Doradus as a bright source of gamma-ray emission in the LMC in addition to fainter emission regions found in the northern part of the galaxy. The gamma-ray emission from the LMC shows very little correlation with gas density and is rather correlated to tracers of massive star forming regions. The close confinement of gamma-ray emission to star forming regions suggests a relatively short GeV cosmic-ray proton diffusion length. Conclusions: The close correlation between cosmic-ray density and massive star tracers supports the idea that cosmic rays are accelerated in massive star forming regions as a result of the large amounts of kinetic energy that are input by the stellar winds and supernova explosions of massive stars into the interstellar medium.

Mots clés: acceleration of particles; cosmic rays; Magellanic Clouds; gamma rays: galaxies

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

A.A. Abdo, Markus Ackermann, Marco Ajello, W. B. Atwood, Luca Baldini, et al.. Observations of the Large Magellanic Cloud with Fermi. Astronomy and Astrophysics - A&A, 2010, 512, pp.A7. ⟨10.1051/0004-6361/200913474⟩. ⟨in2p3-00482693⟩