Attila Abramowski, Felix A. Aharonian, Faical Ait Benkhali, A. G. Akhperjanian, Ekrem Oǧuzhan Angüner, Gisela Anton, Michael Backes, Shangkari Balenderan, Arnim Balzer, Anna Barnacka, Yvonne Becherini, J. Becker Tjus, K. Bernlöhr, E. Birsin, E. Bissaldi, Jonathan Biteau, Markus Boettcher, Catherine Boisson, J. Bolmont, Pol Bordas, J. Brucker, Francois Brun, Pierre Brun, Tomasz Bulik, Svenja Carrigan, Sabrina Casanova, Paula M. Chadwick, R. Chalme-Calvet, Ryan C. G. Chaves, A. Cheesebrough, M. Chretien, Sergio Colafrancesco, Gabriele Cologna, Jan Conrad, C. Couturier, Y. Cui, A. Djannati-Ataï, W. Domainko, G. Dubus, K. Dutson, J. Dyks, M. Dyrda, T. Edwards, Kathrin Egberts, P. Eger, P. Espigat, C. Farnier, S. Fegan, F. Feinstein, M. V. Fernandes, D. Fernandez, A. Fiasson, G. Fontaine, A. Foerster, Matthias Fussling, M. Gajdus, Y. A. Gallant, T. Garrigoux, G. Giavitto, B. Giebels, J. F. Glicenstein, M. -H. Grondin, M. Grudzinska, S. Haeffner, J. Hahn, J. Harris, G. Heinzelmann, G. Henri, G. Hermann, O. Hervet, A. Hillert, James Anthony Hinton, W. Hofmann, P. Hofverberg, M. Holler, D. Horns, A. Jacholkowska, C. Jahn, M. Jamrozy, M. Janiak, F. Jankowsky, I. Jung, M. A. Kastendieck, K. Katarzynski, U. Katz, S. Kaufmann, B. Khelifi, M. Kieffer, S. Klepser, D. Klochkov, W. Kluzniak, T. Kneiske, D. Kolitzus, Nu. Komin, K. Kosack, S. Krakau, F. Krayzel, P. P. Krueger, H. Laffon, G. Lamanna, J. Lefaucheur, A. Lemiere, M. Lemoine-Goumard, J. -P. Lenain, T. Lohse, A. Lopatin, C. -C. Lu, V. Marandon, A. Marcowith, R. Marx, G. Maurin, N. Maxted, M. Mayer, T. J. L. McComb, J. Mehault, P. J. Meintjes, U. Menzler, M. Meyer, R. Moderski, M. Mohamed, E. Moulin, T. Murach, C. L. Naumann, M. de Naurois, J. Niemiec, S. J. Nolan, L. Oakes, H. Odaka, S. Ohm, E. de Ona Wilhelmi, B. Opitz, M. Ostrowski, I. Oya, M. Panter, R. D. Parsons, M. Paz Arribas, N. W. Pekeur, G. Pelletier, J. Perez, P. -O. Petrucci, B. Peyaud, S. Pita, H. Poon, G. Puehlhofer, M. Punch, A. Quirrenbach, S. Raab, M. Raue, I. Reichardt, A. Reimer, O. Reimer, M. Renaud, R. de los Reyes, F. Rieger, L. Rob, C. Romoli, S. Rosier-Lees, G. Rowell, B. Rudak, C. B. Rulten, V. Sahakian, David M. Sanchez, A. Santangelo, R. Schlickeiser, F. Schuessler, A. Schulz, U. Schwanke, S. Schwarzburg, S. Schwemmer, H. Sol, G. Spengler, F. Spies, L. Stawarz, R. Steenkamp, Christian Stegmann, F. Stinzing, K. Stycz, Iurii Sushch, J. -P. Tavernet, T. Tavernier, A. M. Taylor, R. Terrier, M. Tluczykont, C. Trichard, K. Valerius, C. van Eldik, B. van Soelen, G. Vasileiadis, C. Venter, A. Viana, P. Vincent, H. J. Voelk, F. Volpe, M. Vorster, T. Vuillaume, S. J. Wagner, P. Wagner, R. M. Wagner, M. Ward, M. Weidinger, Q. Weitzel, R. White, A. Wierzcholska, P. Willmann, A. Woernlein, D. Wouters, R. Yang, V. Zabalza, M. Zacharias, A. A. Zdziarski, Alraune Zech, H. -S. Zechlin, D. Malyshev

• Context. Very-high-energy (VHE; E > 100 GeV) gamma-ray emission from blazars inevitably gives rise to electron-positron pair production through the interaction of these gamma-rays with the extragalactic background light (EBL). Depending on the magnetic fields in the proximity of the source, the cascade initiated from pair production can result in either an isotropic halo around an initially- beamed source or a magnetically- broadened cascade :aux. Aims. Both extended pair-halo (PH) and magnetically broadened cascade (MBC) emission from regions surrounding the blazars 1ES 1101-232, IRS 0229+200, and PKS 2155-304 were searched for using VHE y-ray data taken with the High Energy Stereoscopic System (HESS.) and high-energy (HE; 100 MeV < E < 100 GeV) gamma-ray data with the Fermi Large Area Telescope (LAT). Methods. By comparing the angular distributions of the reconstructed gamma-ray events to the angular profiles calculated from detailed theoretical models, the presence of PH and MBC was investigated. Results. Upper limits on theContext. Very-high-energy (VHE; E > 100 GeV) gamma-ray emission from blazars inevitably gives rise to electron-positron pair production through the interaction of these gamma-rays with the extragalactic background light (EBL). Depending on the magnetic fields in the proximity of the source, the cascade initiated from pair production can result in either an isotropic halo around an initially- beamed source or a magnetically- broadened cascade :aux. Aims. Both extended pair-halo (PH) and magnetically broadened cascade (MBC) emission from regions surrounding the blazars 1ES 1101-232, IRS 0229+200, and PKS 2155-304 were searched for using VHE y-ray data taken with the High Energy Stereoscopic System (HESS.) and high-energy (HE; 100 MeV < E < 100 GeV) gamma-ray data with the Fermi Large Area Telescope (LAT). Methods. By comparing the angular distributions of the reconstructed gamma-ray events to the angular profiles calculated from detailed theoretical models, the presence of PH and MBC was investigated. Results. Upper limits on the extended emission around lES 1101-232, lES 0229+200, and PKS 2155-304 are found to be at a level of a few per cent of the Crab nebula flux above 1 TeV, depending on the assumed photon index of the cascade emission. Assuming strong extra-Galactic magnetic field (EGME) values, >10(-12) G, this limits the production of pair haloes developing from electromagnetic cascades. For weaker magnetic fields, in which electromagnetic cascades would result in MBCs. EGMF strengths in the range (0.3-3) x 10(-15) G were excluded for PKS 2155-304 at the 99% confidence level, under the assumption of a 1 Mpc coherence length.…