Abell 611. II. X-ray and strong lensing analyses
  We present the results of our analyses of the X-ray emission and of the
strong lensing systems in the relaxed galaxy cluster Abell 611 (z=0.288). We
infer the X-ray mass estimate deriving the density and temperature profiles of
the intra-cluster medium within the radius r ~ 700 kpc through a non-parametric
approach; assuming that the cluster is in hydrostatic equilibrium and adopting
a matter density profile, we can recover the total mass distribution of Abell
611 via the X-ray data. We derive the total projected mass in the central
region of Abell 611 performing a parametric analysis of its strong lensing
features through the publicly available analysis software Lenstool. As a final
step we compare the results obtained with both methods. We derive a good
agreement between the X-ray and strong lensing total mass estimates in the
central region (i.e. within the radius r ~100 kpc), while a marginal
disagreement is found between the two mass estimates when extrapolating the
strong lensing results in the outer spatial range. We suggest that in this case
the X-ray/strong lensing mass disagreement can be explained by an incorrect
estimate of the relative contributions of the baryonic component and of the
dark matter, caused by the intrinsic degeneracy between the different mass
components in the strong lensing analysis. We discuss the effect of some
possible systematic errors that influence both mass estimates. We find a slight
dependence of the measurements of the X-ray temperatures (and therefore of the
X-ray total masses) on the background adopted in the spectral analysis, with
total deviations on the value of M_200 of the order of the 1-sigma statistical
error. The strong lensing mass results are instead sensitive to the
parameterisation of the galactic halo mass in the central regions, in
particular to the modelling of the Brightest Cluster Galaxy (BCG) baryonic
component.
