Gravitational lensing has now become a popular tool to measure the mass
distribution of structures in the Universe on various scales. Here we focus on
the study of galaxy's scale dark matter halos with galaxy-galaxy lensing
techniques: observing the shapes of distant background galaxies which have been
lensed by foreground galaxies allows us to map the mass distribution of the
foreground galaxies. The lensing effect is small compared to the intrinsic
ellipticity distribution of galaxies, thus a statistical approach is needed to
derive some constraints on an average lens population. An advantage of this
method is that it provides a probe of the gravitational potential of the halos
of galaxies out to very large radii, where few classical methods are viable,
since dynamical and hydrodynamical tracers of the potential cannot be found at
this radii. We will begin by reviewing the detections of galaxy-galaxy lensing
obtained so far. Next we will present a maximum likelihood analysis of
simulated data we performed to evaluate the accuracy and robustness of
constraints that can be obtained on galaxy halo properties. Then we will apply
this method to study the properties of galaxies which stand in massive cluster
lenses at z~0.2. The main result of this work is to find dark matter halos of
cluster galaxies to be significantly more compact compared to dark matter halos
around field galaxies of equivalent luminosity, in agreement with early
galaxy-galaxy lensing studies and with theoretical expectations, in particular
with the tidal stripping scenario. We thus provide a strong confirmation of
tidal truncation from a homogeneous sample of galaxy clusters. Moreover, it is
the first time that cluster galaxies are probed successfully using
galaxy-galaxy lensing techniques from ground based data.Comment: 8 pages, 5 figures, to appear in Moriond Proceedings, From Dark Halos
to Ligh