Limitations of model fitting methods for lensing shear estimation

Understand

Gravitational lensing shear has the potential to be the most powerful tool for constraining the nature of dark energy.

• However, accurate measurement of galaxy shear is crucial and has been shown to be non-trivial by the Shear TEsting Programme.
• Here we demonstrate a fundamental limit to the accuracy achievable by model-fitting techniques, if oversimplistic models are used.
• We show that even if galaxies have elliptical isophotes, model-fitting methods which assume elliptical isophotes can have significant biases if they use the wrong profile.