A Distant, X-Ray Luminous Cluster of Galaxies at Redshift 0.83

Details A Distant, X-Ray Luminous Cluster of Galaxies at Redshift 0.83 A Distant, X-Ray Luminous Cluster of Galaxies at Redshift 0.83

Mar 1999

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999stin...9942139d&link_type=abstract

Technical Report, Space Telescope Science Inst. Baltimore, MD United States

Astronomy and Astrophysics

Astrophysics

Galactic Clusters, Red Shift, X Ray Sources, Disk Galaxies, Stellar Evolution, Cosmology, Astrophysics, Perturbation, Rosat Mission, Emission Spectra, Luminosity, Temperature

Scientific paper

We have observed the most distant (= 0.829) cluster of galaxies in the Einstein Extended Medium Sensitivity Survey (EMSS), with the ASCA and ROSAT satellites. We find an X-ray temperature of 12.3(sup 3.1, sub 2.2) keV for this cluster, and the ROSAT map reveals significant substructure. The high temperature of MS1054-0321 is consistent with both its approximate velocity dispersion, based on the redshifts of 12 cluster members we have obtained at the Keck and the Canada-France-Hawaii telescopes, and with its weak lensing signature. The X-ray temperature of this cluster implies a virial mass approximately 7.4 x 1014 /h solar mass, if the mean matter density in the universe equals the critical value (OMEGA0 = 1), or larger if OMEGA0 < 1. Finding such a hot, massive cluster in the EMSS is extremely improbable if clusters grew from Gaussian perturbations in an OMEGA0 = 1 universe. Combining the assumptions that OMEGA0 = 1 and that the initial perturbations were Gaussian with the observed X-ray temperature function at low redshift, we show that this probability of this cluster occurring in the volume sampled by the EMSS is less than a few times 10-5. Nor is MS1054-0321 the only hot cluster at high redshift; the only two other z > 0.5 EMSS clusters already observed with ASCA also have temperatures exceeding 8 keV. Assuming again that the initial perturbations were Gaussian and OMEGA0 = 1, we find that each one is improbable at the < 10-2 level. These observations, along with the fact that these luminosities and temperatures of the high-z clusters all agree with the low-z Lx - Tx relation, argue strongly that OMEGA0 < 1. Otherwise, the initial perturbations must be non-Gaussian, if these clusters' temperatures do indeed reflect their gravitational potentials.

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