Astron. Astrophys. 347, 434-441 (1999)

About the origin of extinction in the gravitational lens system MG J0414+0534 ^*

M.-C. Angonin-Willaime ¹, C. Vanderriest ^{**  2}, F. Courbin ^2,3,4, I. Burud ³, P. Magain ^{***  3} and F. Rigaut <sup>5

1</sup> DEMIRM, Observatoire de Paris-Meudon, France
² UMR 8631, CNRS-DAEC, Observatoire de Paris-Meudon, F-92195 Meudon Cedex, France
³ Institut d'Astrophysique et de Géophysique, Université de Liège, Avenue de Cointe 5, B-4000, Liège, Belgium
⁴ Universidad Catolica de Chile, Department of Astronomy and Astrophysics, Casilla 22, Santiago 22, Chile
⁵ European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München, Germany

Received 21 January 1999 / Accepted 25 March 1999

Abstract

Photometric measurements of the highly reddened gravitational mirage MG J0414+0534 have been carried out either by PSF subtraction or by applying accurate deconvolution algorithms to optical (R, I) and near-infrared (K) images obtained at CFHT and NOT under sub-arcsecond seeing conditions. It is confirmed that the close pair of images A1-A2 suffers a larger extinction than B and C. While the colours of image A2 obtained from ground-based data seem inconsistent with a simple reddening law, higher resolution images available from HST archives reveal an additional extended component (arc) which introduces significant errors in the photometric decomposition. When the arc component is properly taken into account, the colours of the 4 nucleus images do agree with a classical reddening law, with A2 being by far the most obscured component. Such a differential extinction (maximum difference E(R-I) 0.6) is likely due to the lensing galaxy. This does not mean that all the extinction occurs into the lens. Indeed, the fact that the arc is much less red than the images of the nucleus suggests that an important part of the reddening is intrinsic to the source. Finally, no significant variability is observed within this data set, i.e. between 1994 and 1997, while a discrepancy from earlier data is noticed for (A1 + A2).

Key words: galaxies: ISM galaxies: quasars: individual: MG J0414+0534 cosmology: gravitational lensing infrared: galaxies

* Based on observations collected with the Canada-France-Hawaii Telescope at Mauna Kea (Hawaii, USA), the Nordic Optical Telescope (Canary, Spain) and archive data from the Hubble Space Telescope (NASA/ESA)
** Visiting Astronomer, Canada-France-Hawaii Telescope
*** Also Maître de recherches au FNRS, Belgium

Send offprint requests to: M.-C. Angonin-Willaime

SIMBAD Objects

Contents

• 1. Introduction
• 2. Ground-based observations
  • 2.1. Optical: observations and reduction methods
  • 2.2. Comments on the optical photometry
  • 2.3. Infrared
• 3. HST data
  • 3.1. Photometric measurement of the nucleus images
  • 3.2. Comparison of HST and ground-based photometric measurements; influence of an extended structure
• 4. Extinction
  • 4.1. Estimation of the extinction and discussion of its origin
  • 4.2. Consequences
• 5. Conclusion
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: June 30, 1999
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