Issue |
A&A
Volume 524, December 2010
|
|
---|---|---|
Article Number | A77 | |
Number of page(s) | 8 | |
Section | Extragalactic astronomy | |
DOI | https://doi.org/10.1051/0004-6361/201014747 | |
Published online | 24 November 2010 |
Search for an extended VHE γ-ray emission from Mrk 421 and Mrk 501 with the MAGIC Telescope
1
IFAE, Edifici Cn., Campus UAB, 08193
Bellaterra,
Spain
2
INAF National Institute for Astrophysics,
00136
Rome,
Italy
3
Università di Siena, and INFN Pisa, 53100
Siena,
Italy
4
Technische Universität Dortmund, 44221
Dortmund,
Germany
5
Universitat Autònoma de Barcelona, 08193
Bellaterra,
Spain
6
Universidad Complutense, 28040
Madrid,
Spain
7
Università di Padova and INFN, 35131
Padova,
Italy
8
Inst. de Astrofísica de Canarias, 38200 La Laguna,
Tenerife,
Spain
9
University of Łódź, 90236
Lodz,
Poland
10
Tuorla Observatory, University of Turku,
21500
Piikkiö,
Finland
11
Deutsches Elektronen-Synchrotron (DESY),
15738
Zeuthen,
Germany
12
ETH Zurich, 8093
Switzerland
13
Max-Planck-Institut für Physik, 80805
München,
Germany
14
Universitat de Barcelona (ICC/IEEC), 08028
Barcelona,
Spain
15
Universität Würzburg, 97074
Würzburg,
Germany
16
Depto. de Astrofisica, Universidad, 38206 La Laguna, Tenerife, Spain
17
Università di Udine, and INFN Trieste, 33100
Udine,
Italy
18
Institut de Ciències de l’Espai (IEEC-CSIC),
08193
Bellaterra,
Spain
19
Inst. de Astrofísica de Andalucía (CSIC),
18080
Granada,
Spain
20
Croatian MAGIC Consortium, Institute R. Boskovic, University of
Rijeka, University of Split, 10000
Zagreb,
Croatia
21
University of California, Davis, 95616-8677, USA
22
Inst. for Nucl. Research and Nucl. Energy,
1784
Sofia,
Bulgaria
23
INAF/Osservatorio Astronomico and INFN,
34143
Trieste,
Italy
24
ICREA, 08010
Barcelona,
Spain
25
Università di Pisa, and INFN Pisa, 56126
Pisa,
Italy
26
SDC Data Center for Astrophysics, Geneva
Observatory, Chemin d’Écogia
16, 1290
Versoix,
Switzerland
27
APC, 10 rue
Alice Domon et Leonie Duquet, 75205
Paris Cedex 13,
France
†
Corresponding author: R. Mirzoyan, e-mail: razmik@mppmu.mpg.de
‡
Corresponding author: J. Sitarek, e-mail: jsitarek@mppmu.mpg.de
Received:
7
April
2010
Accepted:
12
July
2010
Context. Part of the very high energy γ-ray radiation coming from extragalactic sources is absorbed through the pair production process on the extragalactic background light photons. Extragalactic magnetic fields alter the trajectories of these cascade pairs and, in turn, convert cosmic background photons to γ-ray energies by inverse Compton scattering. These secondary photons can form an extended halo around bright VHE sources.
Aims. We searched for an extended emission around the bright blazars Mrk 421 and Mrk 501 using the MAGIC telescope data.
Methods. If extended emission is present, the angular distribution of reconstructed γ-ray arrival directions around the source is broader than for a point-like source. In the analysis of a few tens of hours of observational data taken from Mrk 421 and Mrk 501 we used a newly developed method that provides better angular resolution. This method is based on the usage of multidimensional decision trees. Comparing the measured shapes of angular distributions with those expected from a point-like source one can detect or constrain possible extended emission around the source. We also studied the influence of different types of systematic errors on the shape of the distribution of reconstructed γ-ray arrival directions for a point source.
Results. We present upper limits for an extended emission calculated for both sources for various source extensions and emission profiles. We obtain upper limits on the extended emission around the Mrk 421 (Mrk 501) on the level of <5% (<4%) of the Crab Nebula flux above the energy threshold of 300 GeV. Using these results we discuss possible constraints on the extragalactic magnetic fields strength around a few times 10-15 G.
Key words: galaxies: active / γ-rays: galaxies
© ESO, 2010
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