Test of parametrized post-Newtonian gravity with galaxy-scale strong lensing systems

Understand

Based on a mass-selected sample of galaxy-scale strong gravitational lenses from the SLACS, BELLS, LSD and SL2S surveys and using a well-motivated fiducial set of lens-galaxy parameters we tested the weak-field metric on kiloparsec scales and found a constraint on the post-Newtonian parameter $\gamma = 0.995^{+0.037}_{-0.047}$ under the assumption of a flat $\Lambda$CDM universe with parameters taken from \textit{Planck} observations.

• General relativity (GR) predicts exactly $\gamma=1$.
• Uncertainties concerning the total mass density profile, anisotropy of the velocity dispersion and the shape of the light-profile combine to systematic uncertainties of $\sim 25\%$.
• By applying a cosmological model independent method to the simulated future LSST data, we found a significant degeneracy between the PPN $\gamma$ parameter and spatial curvature of the Universe.