M 87 at metre wavelengths: the LOFAR picture F. de Gasperin, E. Orrú, M. Murgia, A. Merloni, H. Falcke, R. Beck, R. Beswick, L. Bîrzan, A. Bonafede, M. Brüggen et al. (85 more) A&A, 547 (2012) A56 Published online: 26 October 2012 DOI: 10.1051/0004-6361/201220209