Comparison of Strong Gravitational Lens Model Software III. Direct and indirect semi-independent lens model comparisons of COSMOS J095930+023427, SDSS J1320+1644, SDSSJ1430+4105 and J1000+0021

Abstract: Analysis of strong gravitational lensing data is important in this era of precision cosmology. The objective of the present study is to directly compare the analysis of strong gravitational lens systems using different lens model software and similarly parameterized models to understand the differences and limitations of the resulting models. The software lens model translation tool, HydraLens, was used to generate multiple models for four strong lens systems including COSMOS J095930+023427, SDSS J1320+1644, SDSSJ1430+4105 and J1000+0021. All four lens systems were modeled with PixeLens, Lenstool, glafic, and Lensmodel. The input data and parameterization of each lens model was similar for the four model programs used to highlight differences in the output results. The calculation of the Einstein radius and enclosed mass for each lens model was comparable. The results were more dissimilar if the masses of more than one lens potential were free-parameters. The image tracing algorithms of the software are different, resulting in different output image positions and differences in time delay and magnification calculations, as well as ellipticity and position angle of the resulting lens model. In a comparison of different software versions using identical model input files, results differed significantly when using two versions of the same software. These results further support the need for future lensing studies to include multiple lens models, use of open software, availability of lens model files use in studies, and computer challenges to develop new approaches. Future studies need a standard nomenclature and specification of the software used to allow improved interpretation, reproducibility and transparency of results.