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
  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.
