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http://hdl.handle.net/20.500.12386/24871
Titolo: | Search for Extended Gamma-Ray Emission from the Virgo Galaxy Cluster with FERMI-LAT | Autori: | Ackermann, M. Ajello, M. Albert, A. Atwood, W. B. Baldini, L. Barbiellini, G. Bastieri, D. Bechtol, K. Bellazzini, R. Bissaldi, E. Bloom, E. D. Mizuno, T. Monzani, M. E. Morselli, A. Moskalenko, I. V. Murgia, S. Nuss, E. Ohsugi, T. Orienti, M. Orlando, E. Ormes, J. F. Reimer, O. Paneque, D. Perkins, J. S. Pesce-Rollins, M. Petrosian, V. Piron, F. Pivato, G. Porter, T. A. Rainó, S. Rando, R. Razzano, M. Sánchez-Conde, M. Reimer, A. Schulz, A. Sgró, C. Siskind, E. J. Spada, F. Spandre, G. Spinelli, P. Storm, E. Tajima, H. Bonino, R. Takahashi, H. Thayer, J. B. Torres, D. F. Tosti, G. Troja, E. Vianello, G. Wood, K. S. Wood, M. Zaharijas, G. Zimmer, S. Bottacini, E. Fermi-LAT Collaboration Brandt, T. J. Bregeon, J. Bruel, P. Buehler, R. Buson, S. Caliandro, G. A. Cameron, R. A. Caputo, R. Caragiulo, M. CARAVEO, PATRIZIA Casandjian, J. M. Cavazzuti, E. Cecchi, C. Charles, E. Chekhtman, A. Chiaro, G. Ciprini, S. Cohen-Tanugi, J. Conrad, J. Cutini, S. D'Ammando, F. de Angelis, A. de Palma, F. Desiante, R. Digel, S. W. Di Venere, L. Drell, P. S. Favuzzi, C. Fegan, S. J. Focke, W. B. Franckowiak, A. Fukazawa, Y. Funk, S. Fusco, P. Gargano, F. Gasparrini, D. Giglietto, N. Giordano, F. GIROLETTI, MARCELLO Glanzman, T. Godfrey, G. Gomez-Vargas, G. A. Grenier, I. A. Guiriec, S. Gustafsson, M. Hewitt, J. W. Hill, A. B. Horan, D. Jeltema, T. E. Jogler, T. Johnson, A. S. Kuss, M. Larsson, S. Latronico, L. Li, J. Li, L. Longo, F. Loparco, F. Lovellette, M. N. Lubrano, P. Maldera, S. Malyshev, D. Manfreda, A. Mayer, M. Mazziotta, M. N. Michelson, P. F. |
Data pubblicazione: | 2015 | Rivista: | THE ASTROPHYSICAL JOURNAL | Numero: | 812 | Fascicolo: | 2 | Da pagina:: | 159 | Abstract: | Galaxy clusters are one of the prime sites to search for dark matter (DM) annihilation signals. Depending on the substructure of the DM halo of a galaxy cluster and the cross sections for DM annihilation channels, these signals might be detectable by the latest generation of γ-ray telescopes. Here we use three years of Fermi-Large Area Telescope data, which are the most suitable for searching for very extended emission in the vicinity of the nearby Virgo galaxy cluster. Our analysis reveals statistically significant extended emission which can be well characterized by a uniformly emitting disk profile with a radius of 3° that moreover is offset from the cluster center. We demonstrate that the significance of this extended emission strongly depends on the adopted interstellar emission model (IEM) and is most likely an artifact of our incomplete description of the IEM in this region. We also search for and find new point source candidates in the region. We then derive conservative upper limits on the velocity-averaged DM pair annihilation cross section from Virgo. We take into account the potential γ-ray flux enhancement due to DM sub-halos and its complex morphology as a merging cluster. For DM annihilating into b\bar{b}, assuming a conservative sub-halo model setup, we find limits that are between 1 and 1.5 orders of magnitude above the expectation from the thermal cross section for m<SUB>DM</SUB> ≲ 100 GeV. In a more optimistic scenario, we exclude < σ v> ̃ 3× {10}<SUP>-26</SUP> {{cm}}<SUP>3</SUP> {{{s}}}<SUP>-1</SUP> for m<SUB>DM</SUB> ≲ 40 GeV for the same channel. Finally, we derive upper limits on the γ-ray-flux produced by hadronic cosmic-ray interactions in the inter cluster medium. We find that the volume-averaged cosmic-ray-to-thermal pressure ratio is less than ̃6%. | Acknowledgments: | A.P. is grateful to the Swedish Research Council for financial support. The Fermi -LAT Collaboration acknowledges generous ongoing support from a number of agencies and institutes that have supported both the development and the operation of the LAT as well as scientific data analysis. These include the National Aeronautics and Space Administration and the Department of Energy in the United States, the Commissariat à l’Energie Atomique and the Centre National de la Recherche Scientifique/Institut National de Physique Nucléaire et de Physique des Particules in France, the Agenzia Spaziale Italiana and the Istituto Nazionale di Fisica Nucleare in Italy, the Ministry of Education, Culture, Sports, Science and Technology (MEXT), High Energy Accelerator Research Organization (KEK) and Japan Aerospace Exploration Agency (JAXA) in Japan, and the K. A. Wallenberg Foundation, the Swedish Research Council and the Swedish National Space Board in Sweden. Additional support for science analysis during the operations phase is gratefully acknowledged from the Istituto Nazionale di Astrofisica in Italy and the Centre National d’Études Spatiales in France. Facility: Fermi | URI: | http://hdl.handle.net/20.500.12386/24871 | URL: | https://iopscience.iop.org/article/10.1088/0004-637X/812/2/159 | ISSN: | 0004-637X | DOI: | 10.1088/0004-637X/812/2/159 | Bibcode ADS: | 2015ApJ...812..159A | Fulltext: | open |
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