The origin of peak-offsets in weak-lensing maps
  Centroid positions of peaks identified in weak lensing mass maps often show
offsets with respect to other means of identifying halo centres, like position
of the brightest cluster galaxy or X-ray emission centroid. Here we study the
effect of projected large-scale structure (LSS), smoothing of mass maps, and
shape noise on the weak lensing peak positions. Additionally we compare the
offsets in mass maps to those found in parametric model fits. Using ray-tracing
simulations through the Millennium Run $N$-body simulation, we find that
projected LSS does not alter the weak-lensing peak position within the limits
of our simulations' spatial resolution, which exceeds the typical resolution of
weak lensing maps. We conclude that projected LSS, although a major contaminant
for weak-lensing mass estimates, is not a source of confusion for identifying
halo centres. The typically reported offsets in the literature are caused by a
combination of shape noise and smoothing alone. This is true for centroid
positions derived both from mass maps and model fits.
