SENSITIVITY OF GALAXY CLUSTER MORPHOLOGIES TO OMEGA(0) AND P(K)

We examine the sensitivity of the spatial morphologies of galaxy clust ers to Omega(0) and P(k) using high-resolution N-body simulations with a large dynamic range. Variants of the standard cold dark matter (CDM ) model are considered having different spatial curvatures, SCDM (Omeg a(0) = 1), OCDM (Omega(0) = 0.35), and LCDM (Omega(0) = 0.35, lambda(0 ) = 0.65) and different normalizations, sigma(8). We also explore crit ical density models with different spectral indices, n, of the scale-f ree power spectrum P (k) proportional to k(n). Cluster X-ray morpholog ies are quantified with power ratios (PRs), where we take for the X-ra y emissivity j(gas) proportional to rho(DM)(2), which we argue is a su itable approximation for an analysis X-ray emissivity j(gas) proportio nal to rho(DM)(2), of PRs. We find that Omega(0) primarily influences the means of the PR distributions, whereas the power spectrum (n and s igma(8)) primarily affects their variances: log(10)(P-3/P-0) is the cl eanest probe of Omega(0), since its mean is very sensitive to Omega(0) but very insensitive to P(k). The PR means easily distinguish the SCD M and OCDM models, while the SCDM and LCDM means show a more modest, b ut significant, difference (similar to 3 sigma). The OCDM and LCDM mod els are largely indistinguishable in terms of the PRs. Finally, we com pare these models to a sample of ROSAT clusters and find that the PR m eans of the SCDM clusters exceed the ROSAT means with a high formal le vel of significance (similar to 4 sigma). Though the formal significan ce level of this rho(DM)(2)/X-ray comparison should be considered only approximate, we argue that taking into account the hydrodynamics and cooling will not reconcile a discrepancy this large. The PR means of t he OCDM clusters are consistent, and the means of the LCDM clusters ar e marginally consistent, with those of the ROSAT clusters. Thus, we co nclude that cluster morphologies strongly disfavour Omega = 1 CDM mode ls while favouring low density CDM models (Omega(0) = 0.35) with or wi thout a cosmological constant.