We observed MS 1054 - 0321 , the highest redshift cluster of galaxies in the Einstein Medium Sensitivity Survey ( EMSS ) , with the Chandra ACIS-S detector .
We find the X-ray temperature of the cluster to be 10.4 ^ { +1.7 } _ { -1.5 } keV , lower than , but statistically consistent with , the temperature inferred previously .
This temperature agrees well with the observed velocity dispersion and that found from weak lensing .
We are also able to make the first positive identification of an iron line in this cluster and find a value of 0.26 \pm 0.15 for the abundance relative to solar , consistent with early enrichment of the ICM .
We confirm significant substructure in the form of two distinct clumps in the X-ray distribution .
The eastern clump seems to coincide with the main cluster component .
It has a temperature of 10.5 ^ { +3.4 } _ { -2.1 } keV , approximately the same as the average spectral temperature for the whole cluster .
The western clump is cooler , with a temperature of 6.7 ^ { +1.7 } _ { -1.2 } and may be a subgroup falling into the cluster .
Though the presence of substructure indicates that this cluster is not fully relaxed , cluster simulations suggest that we will underestimate the mass , and we can , therefore , use the mass to constrain \Omega _ { m } .
From the overall cluster X-ray temperature we find the virial mass of the cluster to be at least 4.5 \times 10 ^ { 14 } h ^ { -1 } M _ { \odot } .
We revisit the cosmological implications of the existence of such a hot , massive cluster at a relatively early epoch .
Despite the lower temperature , we still find that the existence of this cluster constrains \Omega _ { m } to be less than one .
If \Omega _ { m } = 1 and assuming Gaussian initial perturbations , we find the probability of observing MS 1054 in the EMSS is \sim 7 \times 10 ^ { -4 } .