TY - JOUR A1 - Husemann, Bernd A1 - Worseck, Gabor A1 - Battaia, Fabrizio Arrigoni A1 - Shanks, T. T1 - Discovery of a dual AGN at z similar or equal to 3.3 with 20 kpc separation JF - Astronomy and astrophysics : an international weekly journal N2 - A prediction of the current paradigm of the hierarchical assembly of galaxies is the presence of supermassive dual black holes at separations of a few kpc or less. In this context, we report the detection of a narrow-line emitter within the extended Ly alpha nebula (similar to 120 kpc diameter) of the luminous radio-quiet quasi-stellar object (QSO) LBQS 0302 0019 at z = 3 : 286. We identify several high-ionization narrow emission lines (He II, C IV, C III) associated with this point-like source, which we have named "Jil", which is only similar to 20 kpc (2 : 0 0 9) away from the QSO in projection. Emission-line diagnostics confirm that the source is likely powered by photoionization of an obscured active galactic nucleus (AGN) three orders of magnitude fainter than the QSO. The system represents the tightest unobscured/obscured dual AGN currently known at z > 3, highlighting the power of MUSE to detect these elusive systems. KW - Techniques: imaging spectroscopy KW - Ultraviolet: ISM KW - galaxies: high-redshift KW - quasars: individual: LBQS 0302-0019 Y1 - 2018 U6 - https://doi.org/10.1051/0004-6361/201732457 SN - 1432-0746 VL - 610 PB - EDP Sciences CY - Les Ulis ER -