[en] We detect a distant cluster of galaxies at z ~1 centered on the QSO lens and luminous X-ray source AXJ2019+112 (Hattori et al 1997). The mass-to-light ratio within an aperture of 0.4 h ^{-1}Mpc determined using the X-ray temperature is M_x / L_V = 190^{+95}_{-66}h(M/L_V)[SUB]sun[/SUB]. The strong lens model yields a compatible value, M/L_V = 315^{+80}_{-80}h(M/L_V)[SUB]sun[/SUB], whereas an independent weak lensing analysis sets an upper limit of M/L_V < 440 h(M/L_V)[SUB]sun[/SUB]. This confirms that AXJ2019+112 has a M/L ratio similar to that of z < 1 massive clusters.
Rosati, P.; European Southern Observatory, D-85748, Garching, Germany
Courbin, F.; Institut d'Astrophysique et de Geophysique, Universite de Liege, 5, Avenue de Cointe, B-4000 Liege, Belgium and URA 173 CNRS-DAEC, Observatoire de Paris, F-92195 Meudon Principal CEDEX, France