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 \sim 10 \% for the DH , while for the galaxy component , they are refined correspondingly by \sim 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 \pm 17 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 \sim 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 .