1704.05380
Hubble Frontier Fields: systematic errors in strong lensing models of galaxy clusters - Implications for cosmography
Acebron, et al
SL by galaxy clusters is a fundamental tool to study DM and constrain the geometry of the Universe. The HST Frontier Fields program has allowed a significant improvement of mass and magnification measurements but lensing models still have a residual RMS between 0.2" and a few arcsecons, not yet completely understood. Systematic errors have to be better understood and treated in order to use strong lensing clusters as reliable cosmological probes. Analysed two simulated HFFs-like clusters from the rubble Frontier Fields Comparison Challenge, Ares and Hera. Use several estimators (relative bias on magnification, density profiles, ellipticity and orientation) to quantify the goodness of the reconstructions by comparing the multiple models, optimized with the parametric SW Lenstool, with the input models. Quantified the impact of systematic errors arising, first, from the choice of different density profiles and configuration and, secondly, from the availability of constraints (spectroscopic or photometric redshifts, redshift ranges of the background sources) in the parametric modeling of strong lensing galaxy clusters and therefore on the retrieval of cosmo parameters. Find that substructures in the outskirts have a significant impact on the position of the multiple images, yielding tighter cosmo contours. The need for wide-field imaging around massive clusters is thus reinforced. Show that competitive cosmological constraints can be obtained also with complex multimodal clusters and that photometric redshifts improve the constraints on cosmological parameters when considering a narrow range of (spectroscopic) redshifts for the sources.
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