A Very Hot High-Redshift Cluster of Galaxies: More Trouble for Ω0 = 1
Abstract
We have observed the most distant (z = 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+3.1-2.2 keV for this cluster, and the ROSAT map reveals significant substructure. The high temperature of MS 1054-0321 is consistent with both its approximate velocity dispersion, based on the redshifts of 12 cluster members that 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 ~7.4 × 1014 h-1 M⊙, if the mean matter density in the universe equals the critical value (Ω0 = 1), or larger if Ω0 < 1. Finding such a hot, massive cluster in the EMSS is extremely improbable if clusters grew from Gaussian perturbations in an Ω0 = 1 universe. Combining the assumptions that Ω0 = 1 and that the intial 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 MS 1054-0321 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 Ω0 = 1, we find that each one is improbable at the less than 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 Ω0 < 1. Otherwise, the initial perturbations must be non-Gaussian, if these clusters' temperatures do indeed reflect their gravitational potentials.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- August 1998
- DOI:
- 10.1086/305923
- arXiv:
- arXiv:astro-ph/9707010
- Bibcode:
- 1998ApJ...502..550D
- Keywords:
-
- COSMOLOGY: OBSERVATIONS;
- COSMOLOGY: DARK MATTER;
- GALAXIES: INTERACTIONS;
- GALAXIES: CLUSTERS: INDIVIDUAL ALPHANUMERIC: MS 1054-;
- 321;
- GALAXIES: INTERGALACTIC MEDIUM;
- X-RAYS: GALAXIES;
- Cosmology: Observations;
- Cosmology: Dark Matter;
- Galaxies: Clusters: Individual: Alphanumeric: MS 1054-0321;
- Galaxies: Interactions;
- Galaxies: Intergalactic Medium;
- X-Rays: Galaxies;
- Astrophysics
- E-Print:
- 20 pages, 4 figures, To appear in 1 Aug 1998 ApJ (heavily revised version of original preprint)