First test of Verlinde's theory of Emergent Gravity using Weak
  Gravitational Lensing measurements
  Verlinde (2016) proposed that the observed excess gravity in galaxies and
clusters is the consequence of Emergent Gravity (EG). In this theory the
standard gravitational laws are modified on galactic and larger scales due to
the displacement of dark energy by baryonic matter. EG gives an estimate of the
excess gravity (described as an apparent dark matter density) in terms of the
baryonic mass distribution and the Hubble parameter. In this work we present
the first test of EG using weak gravitational lensing, within the regime of
validity of the current model. Although there is no direct description of
lensing and cosmology in EG yet, we can make a reasonable estimate of the
expected lensing signal of low redshift galaxies by assuming a background
LambdaCDM cosmology. We measure the (apparent) average surface mass density
profiles of 33,613 isolated central galaxies, and compare them to those
predicted by EG based on the galaxies' baryonic masses. To this end we employ
the ~180 square degrees overlap of the Kilo-Degree Survey (KiDS) with the
spectroscopic Galaxy And Mass Assembly (GAMA) survey. We find that the
prediction from EG, despite requiring no free parameters, is in good agreement
with the observed galaxy-galaxy lensing profiles in four different stellar mass
bins. Although this performance is remarkable, this study is only a first step.
Further advancements on both the theoretical framework and observational tests
of EG are needed before it can be considered a fully developed and solidly
tested theory.
