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

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 <sup>9

1</sup> 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

Abstract

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 035  002 and the intensity ratio / = 1.21  0.25 in the H-band. No other image is detected down to H(5) = 21.3 within 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 around the quasar. We find no such object to a limit of 610^-17 erg cm^{- 2} s^-1. We use the images centered on the deepest absorption lines of the Ly 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 excess 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)

SIMBAD Objects

Contents

• 1. Introduction
• 2. Observations
  • 2.1. Adaptive optics image
  • 2.2. Integral field spectroscopy
• 3. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1998

Online publication: October 22, 1998
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