The CFHTLS-Strong Lensing Legacy Survey (SL2S): Investigating the
  group-scale lenses with the SARCS sample
  We present the Strong Lensing Legacy Survey - ARCS (SARCS) sample compiled
from the final T0006 data release of the Canada-France-Hawaii Telescope Legacy
Survey (CFHTLS) covering a total non-overlapping area of 159 sq.deg. We adopt a
semi-automatic method to find gravitational arcs in the survey that makes use
of an arc-finding algorithm. The candidate list is pruned by visual inspection
and ranking to form the SARCS sample. This list also includes some
serendipitously discovered lens candidates. The SARCS sample consists of 127
lens candidates which span arc radii~2"-18" within the unmasked area of ~ 150
sq. deg. Within the sample, 54 systems are promising lenses amongst which, we
find 12 giant arcs and 2 radial arc candidates. From our sample, we detect a
systematic alignment of giant arcs with the ellipticity of the baryonic
component of the lens in concordance with previous studies. The lens redshift
distribution corresponding to both the giant arcs and all arcs, estimated from
photometric catalogs, peaks at z~0.6. Owing to the large area and depth of the
CFHTLS, we find the largest lens sample probing group-scales for the first
time. We compare the observed image separation distribution (ISD) of our arcs
with theoretical models. A two-component density profile for the lenses which
accounts for both the central galaxy and dark matter component is required by
the data to explain the observed ISD. Unfortunately, current levels of
uncertainties and degeneracies accommodate models both with and without
adiabatic contraction. We also show the effects of changing parameters of the
model that predict the ISD and that a larger lens sample might constrain
relations such as the concentration-mass relation, mass-luminosity relation and
slope of the luminosity function. (abridged)
