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Modélisation de lentilles gravitationnelles et designs optiques non-obstrués pour les sondages grands champs

Abstract : Strong gravitational lenses are an important probe to study the cosmology of the extragalactic universes but gravitational lens modelling is an ill–posed problem. Usually in gravitational lens modelling the lens is described using a parametric model but the background source is not. We improve the existing parametric approach by modelling both the lens and the source using a parametric model. We use a non-singular isothermal ellipsoid model to describe the lens and a Sérsic light profile to describe the source. Our method yields rigorous results on simulated gravitational arcs. We also applied our method to a set of high S/N gravitational arcs in the SL2S and SLACS database. We present the lens and source parameters we obtained for these lenses. Using these parameters we study the distribution of dark matter in galaxy scale halos and the morphology of high redshift sources. We find the fraction of dark matter within the Einstein radius to be 0.2±0.08 and the lens mass present in the core is in the order of 5±2%. Telescopes with unobstructed pupil are known to deliver clean point spread function (PSF) to their focal plane, in contrast to traditional telescopes with obstructed pupil. Recent progress in the manufacturing aspheric surfaces and mounting accuracy favors unobstructed telescopes over obstructed telescopes for science cases that demand stable and clean PSF over the entire field–of–view. We compare the image quality of an unobstructed Three–Mirror–Anastigmat (TMA) design with that of an obstructed TMA. Both the designs have the same primary mirror, effective focal length, field–of–view and detector characteristics. We demonstrate using simulated images of faint elliptical galaxies imaged through the two designs, that both the designs can measure weak lensing observables with same precision, if the PSF is reconstructed within 12 arc-minutes from the source. We also demonstrate that, the unobstructed design delivers desirable precision even if the PSF is reconstructed 50 arc-minutes away from the source.
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https://tel.archives-ouvertes.fr/tel-01091583
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Submitted on : Friday, December 5, 2014 - 4:31:10 PM
Last modification on : Wednesday, April 8, 2020 - 1:48:58 AM
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  • HAL Id : tel-01091583, version 1

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Balasubramanian Singaravelu. Modélisation de lentilles gravitationnelles et designs optiques non-obstrués pour les sondages grands champs. Astrophysique [astro-ph]. Université Paul Sabatier - Toulouse 3, 2014. Français. ⟨tel-01091583⟩

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