Article (Scientific journals)
Redshift estimate of a gravitational lens from the observed reddening of a multiply imaged quasar
Jean, C.; Surdej, Jean
1998In Astronomy and Astrophysics, 339, p. 729-736
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Keywords :
EXTINCTION; GALAXIES: DISTANCES AND REDSHIFTS; QUASARS: INDIVIDUAL: MG 0414+0534; COSMOLOGY: GRAVITATIONAL LENSING; ISM: DUST
Abstract :
[en] Light rays from a multiply imaged quasar usually sample different path lengths across the deflector. Extinction in the lensing galaxy may thus lead to a differential obscuration and reddening between the observed macro-lensed QSO images. These effects naturally depend on the precise shape of the extinction law and on the redshift of the lens. By means of numerical Monte-Carlo simulations, using a least-squares fitting method and assuming an extinction law similar to that observed in the Galaxy, we show how accurate photometric observations of multiply imaged quasars obtained in several spectral bands could lead to the estimate of the lens redshift, irrespective of the visibility of the deflector. Observational requirements necessary to apply this method to real cases are thoroughly discussed. If extinction laws turn out to be too different from galaxy to galaxy, we find out that more promising observations should consist in getting high signal-to-noise low resolution spectra of at least three distinct images of a lensed quasar, over a spectral range as wide as possible, from which it should be straightforward to extract the precise shape of the redshifted extinction law. Very high signal-to-noise, low spectral resolution, VLT observations of H 1413+117 and <ASTROBJ>MG 0414+0534</ASTROBJ> should enable one to derive such a redshifted extinction law.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Jean, C.;  Institut d'Astrophysique, Universitede Liege, Avenue de Cointe 5, B-4000 Liege, Belgium
Surdej, Jean  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS)
Language :
English
Title :
Redshift estimate of a gravitational lens from the observed reddening of a multiply imaged quasar
Publication date :
1998
Journal title :
Astronomy and Astrophysics
ISSN :
0004-6361
eISSN :
1432-0746
Publisher :
EDP Sciences, Les Ulis, France
Volume :
339
Pages :
729-736
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 23 July 2009

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