Triaxiality, principal axis orientation and non-thermal pressure in
  Abell 383
  While clusters of galaxies are regarded as one of the most important
cosmological probes, the conventional spherical modeling of the intracluster
medium (ICM) and the dark matter (DM), and the assumption of strict hydrostatic
equilibrium (i.e., the equilibrium gas pressure is provided entirely by thermal
pressure) are very approximate at best. Extending our previous works, we
developed further a method to reconstruct for the first time the full
three-dimensional structure (triaxial shape and principal axis orientation) of
both DM and intracluster (IC) gas, and the level of non-thermal pressure of the
IC gas. We outline an application of our method to the galaxy cluster Abell
383, taken as part of the CLASH multi-cycle treasury program, presenting
results of a joint analysis of X-ray and strong lensing measurements. We find
that the intermediate-major and minor-major axis ratios of the DM are
0.71+/-0.10 and 0.55+/-0.06, respectively, and the major axis of the DM halo is
inclined with respect to the line of sight of 21.1+/-10.1 deg. The level of
non-thermal pressure has been evaluated to be about 10% of the total energy
budget. We discuss the implications of our method for the viability of the CDM
scenario, focusing on the concentration parameter C and the inner slope of the
DM gamma, since the cuspiness of dark-matter density profiles in the central
regions is one of the critical tests of the cold dark matter (CDM) paradigm for
structure formation: we measure gamma=1.02+/-0.06 on scales down to 25 Kpc, and
C=4.76+/-0.51, values which are close to the predictions of the standard model,
and providing further evidences that support the CDM scenario. Our method
allows us to recover the three-dimensional physical properties of clusters in a
bias-free way, overcoming the limitations of the standard spherical modelling
and enhancing the use of clusters as more precise cosmological probes.
