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Astron. Astrophys. 339, L77-L80 (1998)

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Letter to the Editor

Adaptive optics imaging and integral field spectroscopy of APM 08279+5255: Evidence for gravitational lensing *

Cédric Ledoux 1, Bertrand Théodore 2, Patrick Petitjean 3, 4, Malcolm N. Bremer 3, Geraint F. Lewis ** 5, 6, Rodrigo A. Ibata 7, Michael J. Irwin 8 and Edward J. Totten 9

1 Observatoire Astronomique de Strasbourg, 11 Rue de l'Université, F-67000 Strasbourg, France
2 Service d'Aéronomie du CNRS, BP 3, F-91371 Verrière le Buisson, France
3 Institut d'Astrophysique de Paris - CNRS, 98bis Boulevard Arago, F-75014 Paris, France
4 DAEC, Observatoire de Paris-Meudon, F-92195 Meudon Principal Cedex, France
5 Department of Physics and Astronomy, University of Victoria, Victoria BC, Canada
6 Astronomy Department, University of Washington, Seattle WA, USA
7 European Southern Observatory, Karl-Schwarzschild Strasse 2, D-85748 Garching bei München, Germany
8 Royal Greenwich Observatory, Madingley Road, Cambridge CB3 0EZ, UK
9 Department of Physics, Keele University, Keele, Staffordshire ST5 5BG, UK

Received 1 September 1998 / Accepted 12 September 1998


We report observations of the z = 3.87 broad absorption line quasar APM 08279+5255 (Irwin et al. 1998) with the Adaptive Optics Bonnette (AOB) of the Canada-France-Hawaii Telescope. The object is found to be a double source. The separation of the two images is 0[FORMULA]35 [FORMULA] 0[FORMULA]02 and the intensity ratio [FORMULA]/[FORMULA] = 1.21 [FORMULA] 0.25 in the H-band. No other image is detected down to H(5[FORMULA]) = 21.3 within [FORMULA] from the double image. Strong support for the lensing hypothesis comes from the uniformity of the quasar spectrum as a function of spatial position in the image obtained with the integral field spectrograph OASIS at CFHT. From the 2D-spectroscopy, narrow-band images are reconstructed over the wavelength range 5600-6200 Å to search for emission-line objects in a field of [FORMULA] around the quasar. We find no such object to a limit of 6[FORMULA]10-17 erg cm- 2 s-1. We use the images centered on the deepest absorption lines of the Ly[FORMULA] forest to dim the quasar and to increase the sensitivity closer to the line of sight. One of the images, centered at 5766.4 Å, exhibits a 3[FORMULA] excess [FORMULA] from the quasar to the north-east.

Key words: gravitational lensing – quasars: individual: APM 08279+5255 – quasars: absorption lines

* Based on data collected at the Canada-France-Hawaii Telescope supported by INSU at Mauna Kea, Hawaii (USA).
** Fellow of the Pacific Institute for Mathematical Sciences 1998-1999

Send offprint requests to: C. Ledoux (cedric@astro.u-strasbg.fr)

© European Southern Observatory (ESO) 1998

Online publication: October 22, 1998