Fermi Large Area Telescope observations of the supernova remnant G8.7-0.1

M. Ajello, A. Allafort, L. Baldini, J. Ballet, G. Barbiellini, D. Bastieri, K. Bechtol, R. Bellazzini, B. Berenji, R. D. Blandford, E. D. Bloom, E. Bonamente, A. W. Borgland, J. Bregeon, M. Brigida, P. Bruel, R. Buehler, S. Buson, G. A. Caliandro, R. A. CameronP. A. Caraveo, J. M. Casandjian, C. Cecchi, E. Charles, A. Chekhtman, S. Ciprini, R. Claus, J. Cohen-Tanugi, S. Cutini, A. De Angelis, F. De Palma, C. D. Dermer, E. Do Couto E Silva, P. S. Drell, A. Drlica-Wagner, R. Dubois, C. Favuzzi, S. J. Fegan, E. C. Ferrara, W. B. Focke, M. Frailis, Y. Fukazawa, Y. Fukui, P. Fusco, F. Gargano, D. Gasparrini, S. Germani, N. Giglietto, P. Giommi, F. Giordano, M. Giroletti, T. Glanzman, G. Godfrey, J. E. Grove, S. Guiriec, D. Hadasch, Y. Hanabata, A. K. Harding, K. Hayashi, E. Hays, R. Itoh, G. Jóhannesson, A. S. Johnson, T. Kamae, H. Katagiri, J. Kataoka, J. Knödlseder, H. Kubo, M. Kuss, J. Lande, L. Latronico, S. H. Lee, A. M. Lionetto, F. Longo, F. Loparco, M. N. Lovellette, P. Lubrano, M. N. Mazziotta, J. Mehault, P. F. Michelson, T. Mizuno, A. A. Moiseev, C. Monte, M. E. Monzani, A. Morselli, I. V. Moskalenko, S. Murgia, T. Nakamori, M. Naumann-Godo, S. Nishino, P. L. Nolan, J. P. Norris, E. Nuss, M. Ohno, T. Ohsugi, A. Okumura, N. Omodei, E. Orlando, J. F. Ormes, D. Paneque, D. Parent, V. Pelassa, M. Pesce-Rollins, M. Pierbattista, F. Piron, T. A. Porter, S. Rainò, R. Rando, A. Reimer, O. Reimer, T. Reposeur, M. Roth, H. F.W. Sadrozinski, C. Sgrò, E. J. Siskind, P. D. Smith, G. Spandre, P. Spinelli, D. J. Suson, H. Tajima, H. Takahashi, T. Tanaka, J. G. Thayer, J. B. Thayer, L. Tibaldo, O. Tibolla, D. F. Torres, G. Tosti, A. Tramacere, E. Troja, Y. Uchiyama, T. Uehara, T. L. Usher, J. Vandenbroucke, A. Van Etten, V. Vasileiou, G. Vianello, N. Vilchez, V. Vitale, A. P. Waite, P. Wang, B. L. Winer, K. S. Wood, H. Yamamoto, R. Yamazaki, Z. Yang, H. Yasuda, M. Ziegler, S. Zimmer

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35 Citations (Scopus)

Abstract

We present a detailed analysis of the GeV gamma-ray emission toward the supernova remnant (SNR) G8.7-0.1 with the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. An investigation of the relationship between G8.7-0.1 and the TeV unidentified source HESS J1804-216 provides us with an important clue on diffusion process of cosmic rays if particle acceleration operates in the SNR. TheGeV gamma-ray emission is extended with most of the emission in positional coincidence with the SNR G8.7-0.1 and a lesser part located outside the western boundary of G8.7-0.1. The region of the gamma-ray emission overlaps spatially connected molecular clouds, implying a physical connection for the gamma-ray structure. The total gamma-ray spectrum measured with LAT from 200MeV-100GeV can be described by a broken power-law function with a break of 2.4 ± 0.6 (stat) ± 1.2 (sys)GeV, and photon indices of 2.10 ± 0.06 (stat) ± 0.10 (sys) below the break and 2.70 ± 0.12 (stat) ± 0.14 (sys) above the break. Given the spatial association among the gamma rays, the radio emission of G8.7-0.1, and the molecular clouds, the decay of π0s produced by particles accelerated in the SNR and hitting the molecular clouds naturally explains theGeV gamma-ray spectrum. We also find that theGeV morphology is not well represented by the TeV emission from HESS J1804-216 and that the spectrum in theGeV band is not consistent with the extrapolation of the TeV gamma-ray spectrum. The spectral index of the TeV emission is consistent with the particle spectral index predicted by a theory that assumes energy-dependent diffusion of particles accelerated in an SNR. We discuss the possibility that the TeV spectrum originates from the interaction of particles accelerated in G8.7-0.1 with molecular clouds, and we constrain the diffusion coefficient of the particles.

Original languageEnglish
Article number80
JournalAstrophysical Journal
Volume744
Issue number1
DOIs
Publication statusPublished - 2012 Jan 1

Keywords

  • ISM: individual objects (G8.7?0.1, HESS J1804?216)
  • ISM: supernova remnants
  • acceleration of particles
  • cosmic rays
  • gamma rays: ISM

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Ajello, M., Allafort, A., Baldini, L., Ballet, J., Barbiellini, G., Bastieri, D., Bechtol, K., Bellazzini, R., Berenji, B., Blandford, R. D., Bloom, E. D., Bonamente, E., Borgland, A. W., Bregeon, J., Brigida, M., Bruel, P., Buehler, R., Buson, S., Caliandro, G. A., ... Zimmer, S. (2012). Fermi Large Area Telescope observations of the supernova remnant G8.7-0.1. Astrophysical Journal, 744(1), [80]. https://doi.org/10.1088/0004-637X/744/1/80