Mathematics – Logic
Scientific paper
Dec 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994aas...18511902m&link_type=abstract
American Astronomical Society, 185th AAS Meeting, #118.07; Bulletin of the American Astronomical Society, Vol. 26, p.1516
Mathematics
Logic
Scientific paper
We use a representative sample of galaxy clusters to constrain the range of cluster X-ray morphologies. After developing and testing quantitative, objective, and reproducible measures of cluster X-ray morphology, we apply these measures to a sample of 65\ Einstein IPC cluster observations to constrain the intrinsic distributions of (i) emission weighted centroid variation w_{vec x}, (ii) emission weighted axial ratio eta , (iii) emission weighted orientation theta_o , and (iv) measures of the radial fall--off, alpha and beta . For each cluster we use a Monte--Carlo procedure to determine the effects of Poisson noise, detector imperfections, and foreground/background X-ray point sources. We then use the range of cluster X-ray morphology to constrain three generic cosmological models (Omega =1, Omega_o =0.2, and Omega_o =0.2 & lambda_o =0.8). We evolve eight sets of Gaussian random initial conditions consistent with an effective power spectrum P(k)~ k(-1) on cluster scales. Using a sample of 24 numerical cluster simulations (3times8 ) which include gravity and gas physics (but no cooling or ejection from galaxies), we compare observed cluster X-ray morphologies with the X-ray morphologies of clusters simulated with different underlying cosmological models. Specifically, we build artificial ensembles with the same distributions in the number of cluster photons, X-ray temperature, and cluster redshift as the\ Einstein ensemble; we then compare the observed and simulated distributions in w_{vec x}, eta , and alpha . The comparisons indicate that (i) these three morphological characteristics are sensitive to the underlying cosmological model, and (ii) galaxy clusters with the observed range of X-ray morphology are very unlikely in low Omega_o cosmologies. The analysis favors the Omega =1 model, though some discrepancies remain. We discuss the effects of changing the initial conditions and of including additional physics in the simulations.
Evrard August E.
Fabricant Dan G.
Geller Margaret J.
Mohr Joseph John
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