Gamma-Ray Emission from the Shell of Supernova Remnant W44 Revealed by the Fermi LAT

• Published in: Science (American Association for the Advancement of Science) 2010-02, Vol.327 (5969), p.1103-1106
• Main Authors: Abdo, A.A, Ajello, M, Barbiellini, G, Bastieri, D, Bechtol, K, Berenji, B, Bonamente, E, Borgland, A.W, Burnett, T.H, Caliandro, G.A, Caraveo, P.A, Casandjian, J.M, Cecchi, C, Chiang, J, Ciprini, S, Cognard, I, Cominsky, L.R, Cutini, S, Dermer, C.D, de Angelis, A, do Couto e Silva, E, Dumora, D, Espinoza, C, Farnier, C, Favuzzi, C, Focke, W.B, Fortin, P, Fukazawa, Y, Funk, S, Gehrels, N, Giebels, B, Giglietto, N, Godfrey, G, Grenier, I.A, Grondin, M.-H, Grove, J.E, Guillemot, L, Guiriec, S, Hanabata, Y, Hayashida, M, Jackson, M.S, Jóhannesson, G, Johnson, A.S, Johnson, T.J, Johnson, W.N, Kamae, T, Katagiri, H, Kataoka, J, Katsuta, J, Kawai, N, Kerr, M, Knödlseder, J, Kramer, M, Longo, F, Loparco, F, Lott, B, Lovellette, M.N, Lubrano, P, Madejski, G.M, Mazziotta, M.N, Meurer, C, Monte, C, Monzani, M.E, Morselli, A, Moskalenko, I.V, Norris, J.P, Nuss, E, Ohsugi, T, Ormes, J.F, Parent, D, Pelassa, V, Pesce-Rollins, M, Piron, F, Razzano, M, Reimer, A, Reimer, O, Rochester, L.S, Romani, R.W, Ryde, F, Sadrozinski, H.F.-W, Sander, A, Sgrò, C, Siskind, E.J, Smith, D.A, Smith, P.D, Stappers, B.W, Stecker, F.W, Strickman, M.S, Suson, D.J, Tajima, H, Takahashi, H, Thayer, J.G, Tibolla, O, Torres, D.F, Tramacere, A, Venter, C, Vilchez, N, Wood, K.S, Yamazaki, R, Ylinen, T
• Format: Article
• Language: English
• Subjects: area telescope; Astronomi och astrofysik; Astronomy; Astronomy and astrophysics; Astrophysics; Cosmic rays (including sources, origin, acceleration, and interactions); cosmic-rays; Earth, ocean, space; Electrons; Emission spectra; Exact sciences and technology; Fysik; galactic plane; Gamma rays; High Energy Astrophysical Phenomena; Interstellar medium (ism) and nebulae in milky way; j1713.7-3946; NATURAL SCIENCES; NATURVETENSKAP; Particle acceleration; Particle emission; Particle physics; Photons; Physics; Pollutant emissions; Protons; pulsar wind nebula; Sciences of the Universe; shocked molecular gas; Stellar systems. Galactic and extragalactic objects and systems. The universe; streaming instability; Supernova remnants; Supernovae; Unidentified sources and radiation outside the solar system; very-high-energy; wave dissipation
• ISSN: 0036-8075; 1095-9203; 1095-9203
• DOI: 10.1126/science.1182787

Recent observations of supernova remnants (SNRs) hint that they accelerate cosmic rays to energies close to approximately 10¹⁵ electron volts. However, the nature of the particles that produce the emission remains ambiguous. We report observations of SNR W44 with the Fermi Large Area Telescope at energies between 2 x 10⁸ electron volts and 3 x10¹¹ electron volts. The detection of a source with a morphology corresponding to the SNR shell implies that the emission is produced by particles accelerated there. The gamma-ray spectrum is well modeled with emission from protons and nuclei. Its steepening above approximately 10⁹ electron volts provides a probe with which to study how particle acceleration responds to environmental effects such as shock propagation in dense clouds and how accelerated particles are released into interstellar space.