Galaxy halo truncation and Giant Arc Surface Brightness Reconstruction
  in the Cluster MACSJ1206.2-0847
  In this work we analyze the mass distribution of MACSJ1206.2-0847, especially
focusing on the halo properties of its cluster members. The cluster appears
relaxed in its X-ray emission, but has significant amounts of intracluster
light which is not centrally concentrated, suggesting that galaxy-scale
interactions are still ongoing despite the overall relaxed state. The cluster
lenses 12 background galaxies into multiple images and one galaxy at $z=1.033$
into a giant arc and its counterimage. The multiple image positions and the
surface brightness distribution (SFB) of the arc which is bent around several
cluster members are sensitive to the cluster galaxy halo properties. We model
the cluster mass distribution with a NFW profile and the galaxy halos with two
parameters for the mass normalization and extent of a reference halo assuming
scalings with their observed NIR--light. We match the multiple image positions
at an r.m.s. level of $0.85\arcsec$ and can reconstruct the SFB distribution of
the arc in several filters to a remarkable accuracy based on this cluster
model. The length scale where the enclosed galaxy halo mass is best constrained
is about 5 effective radii -- a scale in between those accessible to dynamical
and field strong lensing mass estimates on one hand and galaxy--galaxy weak
lensing results on the other hand. The velocity dispersion and halo size of a
galaxy with $m_{\rm 160W,AB}=19.2$ or $M_{\rm B,Vega}=-20.7$ are $\sigma=150
\rm kms^{-1}$ and $r\approx 26\pm 6 \rm kpc$, indicating that the halos of the
cluster galaxies are tidally stripped. We also reconstruct the unlensed source
(which is smaller by a factor of $\sim5.8$ in area), demonstrating the increase
of morphological information due to lensing and conclude that this galaxy has
likely star--forming spiral arms with a red (older) central component.
