References 417Figure 14.12.The radial mass profiles determined from the x-ray and lensing analysis for
Abell 2163. The triangles display the total mass profile determined from the x-ray data.
The filled squares are the weak lensing estimates ‘corrected’ for the mean surface density
in the control annulus determined from the x-ray data. The conversion from angular to
physical units is 60′′= 0. 127 h−^1 Mpc (taken from Squireset al1997 [66]).
that the lensing mass estimates are systematically lower by a factor of∼2than
the x-ray results, but generally the results are consistent with each other, given
the substantial uncertainties. There are reasons that the lensing estimate may
be biased downward. Correcting for this gives the results displayed by open
squares. The agreement between the lensing and x-ray results then becomes quite
impressive. The rate and quality of such data will increase dramatically during the
coming years. With weak lensing one can also test the dynamical state of clusters.
By selecting the relaxed ones one can then determine, with some confidence, the
relative distributions of gas and dark matter.
In addition, it will become possible to extend the investigations to
supercluster scales, with the aim of determining the power spectrum and obtain
information on the cosmological parameters [63, 64].
References
[1] Perlmutter Set al 1999 Astrophys. J. 517565
[2] Trimble V 1987Annu. Rev. Astron. Astrophys. 25425
[3] Zwicky F 1933Helv. Phys. Acta 6110