Sensitivity of Galaxy Cluster Morphologies to Omega_0 and P(k)

Abstract

We examine the sensitivity of the spatial morphologies of galaxy clusters to Omega_0 and P(k) using high-resolution N-body simulations with large dynamic range. Variants of the standard CDM model are considered having different spatial curvatures, SCDM (Omega_0=1), OCDM (Omega_0=0.35), LCDM (Omega_0=0.35, lambda_0=0.65), and different normalizations, sigma_8. We also explore critical density models with different spectral indices, n, of the scale-free power spectrum, P(k) propto k^n. Cluster X-ray morphologies are quantified with power ratios (PRs), where we take for the X-ray emissivity j_gas propto rho^2_DM, which we argue is a suitable approximation for analysis of PRs. We find that Omega_0 primarily influences the means of the PR distributions whereas the power spectrum (n and sigma_8) primarily affects their variances: log_10(P_3/P_0) is the cleanest 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 SCDM and OCDM models, while the SCDM and LCDM means show a more modest, but significant, difference (3 sigma). The OCDM and LCDM models are largely indistinguishable in terms of the PRs. Finally, we compared these models to a sample of ROSAT clusters and find that the cluster morphologies strongly disfavor Omega_0=1, CDM while favoring low density, CDM models with or without a cosmological constant.