MAGIC observations of the giant radio galaxy M 87 in a low-emission state between 2005 and 2007

• Published in: Astronomy and astrophysics (Berlin) 2012-08, Vol.544, p.A96
• Main Authors: Aleksić, J., Alvarez, E. A., Antonelli, L. A., Antoranz, P., Asensio, M., Backes, M., Bastieri, D., Bednarek, W., Biland, A., Bock, R. K., Bonnoli, G., Borla Tridon, D., Braun, I., Bretz, T., Cañellas, A., Colin, P., Contreras, J. L., Cortina, J., Cossio, L., Dazzi, F., De Angelis, A., De Caneva, G., Delgado Mendez, C., Doert, M., Domínguez, A., Dorner, D., Doro, M., García López, R. J., Garczarczyk, M., Garrido, D., Giavitto, G., Godinović, N., Häfner, D., Herrero, A., Kellermann, H., Klepser, S., Krähenbühl, T., Krause, J., Leonardo, E., López, M., López-Oramas, A., Makariev, M., Maneva, G., Maraschi, L., Mariotti, M., Martínez, M., Meucci, M., Miyamoto, H., Moldón, J., Munar-Adrover, P., Nieto, D., Nilsson, K., Orito, R., Oya, I., Paneque, D., Paoletti, R., Pardo, S., Paredes, J. M., Partini, S., Pauss, F., Perez-Torres, M. A., Persic, M., Peruzzo, L., Prada, F., Prada Moroni, P. G., Prandini, E., Reichardt, I., Rhode, W., Rico, J., Rügamer, S., Saito, T. Y., Scapin, V., Schultz, C., Shayduk, M., Shore, S. N., Sillanpää, A., Spanier, F., Spiro, S., Stamerra, A., Steinke, B., Storz, J., Strah, N., Surić, T., Takalo, L., Takami, H., Temnikov, P., Terzić, T., Tescaro, D., Teshima, M., Tibolla, O., Torres, D. F., Treves, A., Uellenbeck, M., Vankov, H., Vogler, P., Wagner, R. M., Zabalza, V., Zandanel, F., Zanin, R., Ghisellini, G.
• Format: Article
• Language: English
• Subjects: Astronomy; Earth, ocean, space; Exact sciences and technology; galaxies: individual: M 87; gamma rays: galaxies
• ISSN: 0004-6361; 1432-0746
• DOI: 10.1051/0004-6361/201117827

Context. We present the results of a long M 87 monitoring campaign in very high energy γ-rays with the MAGIC-I Cherenkov telescope. Aims. We aim to model the persistent non-thermal jet emission by monitoring and characterizing the very high energy γ-ray emission of M 87 during a low state. Methods. A total of 150 h of data were taken between 2005 and 2007 with the single MAGIC-I telescope, out of which 128.6 h survived the data quality selection. We also collected data in the X-ray and Fermi-LAT bands from the literature (partially contemporaneous). Results. No flaring activity was found during the campaign. The source was found to be in a persistent low-emission state, which was at a confidence level of 7σ. We present the spectrum between 100 GeV and 2 TeV, which is consistent with a simple power law with a photon index Γ = 2.21 ± 0.21 and a flux normalization at 300 GeV of (7.7 ± 1.3) × 10-8 TeV-1 s-1 m-2. The extrapolation of the MAGIC spectrum into the GeV energy range matches the previously published Fermi-LAT spectrum well, covering a combined energy range of four orders of magnitude with the same spectral index. We model the broad band energy spectrum with a spine layer model, which can satisfactorily describe our data.