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 Multiple Mirror TelescopeHectospec to separate the galaxy and the smooth dark halo (DH) lensingcontributions. While lensing usually constrains the overall projectedmass density the innovative use of velocity dispersion measurements asa proxy for masses of individual cluster members breaks inherentdegeneracies and allows us to (a) refine the constraints on singlegalaxy masses and on the galaxy mass-to-light scaling relation and as aresult (b) refine the constraints on the DM-only map a high-end goalof lens modelling. The knowledge of cluster member velocity dispersionsimproves the fit by 17 per cent in terms of the image reproductionχ^2 or 20 per cent in terms of the rms. The constraintson the mass parameters improve by ˜10 per cent for the DH whilefor the galaxy component they are refined correspondingly by ˜50per cent including the galaxy halo truncation radius. For an L* galaxywith M^{*}_B=-20.96 for example we obtain best-fittingtruncation radius r_tr^{*}=20.5^{+9.6}_{-6.7} kpc and velocitydispersion σ_* = 324 ± 17 km s^-1.Moreover by performing the surface brightness reconstruction of thesouthern giant arc we improve the constraints on r_tr of twonearby cluster members which have measured velocity dispersions bymore than ˜30 per cent. We estimate the stripped mass for thesetwo galaxies getting results that are consistent with numericalsimulations. In the future we plan to apply this analysis to othergalaxy clusters for which velocity dispersions of member galaxies areavailable.