Galaxy-galaxy lensing in the outskirts of CLASH clusters: constraints on
  local shear and testing mass-luminosity scaling relation
  We present a selection of 24 candidate galaxy-galaxy lensing (GGLs)
identified from Hubble images in the outskirts of the massive galaxy clusters
from the CLASH survey. These GGLs provide insights into the mass distributions
at larger scales than the strong lensing region in the cluster cores. We built
parametric mass models for three of these GGLs showing simple lensing
configurations, in order to assess the properties of their lens and its
environment. We show that the local shear estimated from the GGLs traces the
gravitational potential of the clusters at 1-2 arcmin radial distance, allowing
us to derive their velocity dispersion. We also find a good agreement between
the strength of the shear measured at the GGL positions through strong-lensing
modelling and the value derived independently from a weak-lensing analysis of
the background sources. Overall, we show the advantages of using single GGL
events in the outskirts of clusters to robustly constrain the local shear, even
when only photometric redshift estimates are known for the source. We argue
that the mass-luminosity scaling relation of cluster members can be tested by
modelling the GGLs found around them, and show that the mass parameters can
vary up to $\sim$30% between the cluster and GGL models assuming this scaling
relation.
