Measuring galaxy-galaxy-galaxy-lensing with higher precision and
  accuracy
  Galaxy-galaxy-galaxy lensing (G3L) is a powerful tool for constraining the
three-point correlation between the galaxy and matter distribution and thereby
models of galaxy evolution. We propose three improvements to current
measurements of G3L: (i) a weighting of lens galaxies according to their
redshift difference, (ii) adaptive binning of the three-point correlation
function, and (iii) accounting for the effect of lens magnification by the
cosmic large-scale structure. Improvement (i) is designed to improve the
precision of the G3L measurement, whereas improvements (ii) and (iii) remove
biases of the estimator. We further show how the G3L signal can be converted
from angular into physical scales. The improvements were tested on simple mock
data and simulated data based on the Millennium Run with an implemented
semi-analytic galaxy model. Our improvements increase the signal-to-noise ratio
by 35 % on average at angular scales between 0.1 arcmin and 10 arcmin and
physical scales between $0.02$ and $2 \, h^{-1}\, \textrm{Mpc}$. They also
remove the bias of the G3L estimator at angular scales below 1 arcmin, which
was originally up to 40 %. The signal due to lens magnification is
approximately 10 % of the total signal.
