Constraining the galaxy mass content in the core of A383 using velocity
  dispersion measurements for individual cluster members
  We use velocity dispersion measurements of 21 individual cluster members in
the core of Abell 383, obtained with MMT Hectospec, to separate the galaxy and
the smooth dark halo (DH) lensing contributions. While lensing usually
constrains the overall, projected mass density, the innovative use of velocity
dispersion measurements as a proxy for masses of individual cluster members
breaks inherent degeneracies and allows us to (a) refine the constraints on
single galaxy masses and on the galaxy mass-to-light scaling relation and, as a
result, (b) refine the constraints on the DM-only map, a high-end goal of lens
modelling. The knowledge of cluster member velocity dispersions improves the
fit by 17% in terms of the image reproduction $\chi^2$, or 20% in terms of the
rms. The constraints on the mass parameters improve by ~10% for the DH, while
for the galaxy component, they are refined correspondingly by ~50%, including
the galaxy halo truncation radius. For an L$^*$ galaxy with M$^*_B$=-20.96, for
example, we obtain best fitting truncation radius r$^*_{tr}=20.5^{+9.6}_{-6.7}$
kpc and velocity dispersion $\sigma^*=324\pm17 km/s$. Moreover, by performing
the surface brightness reconstruction of the southern giant arc, we improve the
constraints on r$_{tr}$ of two nearby cluster members, which have measured
velocity dispersions, by more than ~30%. We estimate the stripped mass for
these two galaxies, getting results that are consistent with numerical
simulations. In the future, we plan to apply this analysis to other galaxy
clusters for which velocity dispersions of member galaxies are available.
