Clusters of galaxies are uniquely important cosmological probes of the evolution of the large scale structure , whose diagnostic power depends quite significantly on the ability to reliably determine their masses .
Clusters are typically modeled as spherical systems whose intracluster gas is in strict hydrostatic equilibrium ( i.e. , the equilibrium gas pressure is provided entirely by thermal pressure ) , with the gravitational field dominated by dark matter , assumptions that are only rough approximations .
In fact , numerical simulations indicate that galaxy clusters are typically triaxial , rather than spherical , and that turbulent gas motions ( induced during hierarchical merger events ) provide an appreciable pressure component .
Extending our previous work , we present results of a joint analysis of X-ray , weak and strong lensing measurements of Abell 1689 .
The quality of the data allows us to determine both the triaxial shape of the cluster and the level of non-thermal pressure that is required if the intracluster gas is in hydrostatic equilibrium .
We find that the dark matter axis ratios are 1.24 \pm 0.13 and 2.02 \pm 0.01 on the plane of the sky and along the line of sight , respectively , and that about 20 \% of the pressure is non-thermal .
Our treatment demonstrates that the dynamical properties of clusters can be determined in a ( mostly ) bias-free way , enhancing the use of clusters as more precise cosmological probes .