Reference : Three photometric methods tested on ground-based data of Q 2237+0305
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/6727
Three photometric methods tested on ground-based data of Q 2237+0305
English
Burud, I. [Institut d'Astrophysique, Université de Liège, Avenue de Cointe 5, B-4000 Liège, Belgium; Institute of Theoretical Astrophysics, University of Oslo, Pb. 1029 Blindern, N-0315 Oslo, Norway]
Stabell, R. [ > > ]
Magain, Pierre mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique et traitement de l'image >]
Courbin, F. [Hamburger Sternwarte, Gojenbergsweg 112, D-21029 Hamburg, Germany]
Ostensen, R. [Institut d'Astrophysique, Université de Liège, Avenue de Cointe 5, B-4000 Liège, Belgium; URA 173 CNRS-DAEC, Observatoire de Paris, F-92195 Meudon Principal C{e}dex, France]
Refsdal, S. [Institut d'Astrophysique, Université de Liège, Avenue de Cointe 5, B-4000 Liège, Belgium; Department of Physics, University of Tromso, N-9037 Tromso, Norway]
Remy, M. [ > > ]
Teuber, J. [Institut d'Astrophysique, Université de Liège, Avenue de Cointe 5, B-4000 Liège, Belgium]
1-Nov-1998
Astronomy and Astrophysics
EDP Sciences
339
701-708
Yes (verified by ORBi)
International
0004-6361
1432-0746
Les Ulis
France
[en] QUASARS: INDIVIDUAL: Q 2237+0305 ; GRAVITATIONAL LENSING ; TECHNIQUES: IMAGE PROCESSING
[en] The Einstein Cross, Q 2237+0305, has been photometrically observed in four bands on two successive nights at NOT (La Palma, Spain) in October 1995. Three independent algorithms have been used to analyse the data: an automatic image decomposition technique, a CLEAN algorithm and the new MCS deconvolution code. The photometric and astrometric results obtained with the three methods are presented. No photometric variations were found in the four quasar images. Comparison of the photometry from the three techniques shows that both systematic and random errors affect each method. When the seeing is worse than 1farcs0 , the errors from the automatic image decomposition technique and the Clean algorithm tend to be large (0.04-0.1 magnitudes) while the deconvolution code still gives accurate results (1sigma error below 0.04) even for frames with seeing as bad as 1farcs7 . Reddening is observed in the quasar images and is found to be compatible with either extinction from the lensing galaxy or colour dependent microlensing. The photometric accuracy depends on the light distribution used to model the lensing galaxy. In particular, using a numerical galaxy model, as done with the MCS algorithm, makes the method less seeing dependent. Another advantage of using a numerical model is that eventual non-homogeneous structures in the galaxy can be modeled. Finally, we propose an observational strategy for a future photometric monitoring of the Einstein Cross. Based on observations obtained at NOT, La Palma.
Researchers ; Professionals
http://hdl.handle.net/2268/6727
http://adsabs.harvard.edu/abs/1998A%26A...339..701B
http://arxiv.org/abs/astro-ph/9809107

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