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Astron. Astrophys. 358, 88-94 (2000)

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The sources of extended continuum emission towards Q0151+048A: the host galaxy and the damped Ly[FORMULA] absorber *

J.U. Fynbo 1,2, I. Burud 3 and P. Moller 2

1 Institute of Physics and Astronomy, University of Å rhus, 8000 Å rhus C, Denmark
2 European Southern Observatory, Karl-Schwarzschild-Strasse 2, 85748 Garching by München, Germany
3 Institut d'Astrophysique et de Geophysique de Liège, Université de Liège, Avenue de Cointe 5, 4000 Liège, Belgium

Received 16 November 1999 / Accepted 28 March 2000


We present deep imaging in the U, B and I bands obtained under excellent seeing conditions of the double quasar Q0151+048A,B and of the Damped Ly[FORMULA] (DLA) absorbing galaxy at [FORMULA] named S4.

We analyse the data employing two separate and independent methods. First we deconvolve the images using the MCS algorithm, secondly we decompose the images via an object based iteration process where we fit models to objects without any attempt to improve the resolution of the data. Our detailed analysis of the images reveals, somewhat surprisingly, that extended objects centred on the quasars themselves are much brighter continuum sources than the DLA galaxy.

Due to the complexity caused by the many superimposed objects, we are unable to certify whether or not continuum emission from the DLA galaxy is detected. Continuum emission from the extended objects centred on the positions of the quasars is clearly seen, and the objects are tentatively identified as the "host galaxies" of the quasars. The flux of those host galaxies is of order 2-6% of the quasar flux, and the light profile of the brighter of the two is clearly best fit with a de Vaucouleurs profile. We discuss two alternative interpretations of the origin of the extended flux: i) the early stage of a massive elliptical galaxy in the process of forming the bulk of its stars, and ii) quasar light scattered by dust.

Key words: methods: data analysis – galaxies: intergalactic medium – galaxies: quasars: absorption lines – galaxies: quasars: general – galaxies: photometry – galaxies: quasars: individual: Q0151+048

* Based on observations made with the Nordic Optical Telescope, operated on the island of La Palma jointly by Denmark, Finland, Iceland, Norway, and Sweden, in the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias.

Send offprint requests to: J.U. Fynbo

Correspondence to: jfynbo@obs.aau.dk

© European Southern Observatory (ESO) 2000

Online publication: June 26, 2000