Astronomy and Astrophysics – Astronomy
Scientific paper
May 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993aas...182.7707m&link_type=abstract
American Astronomical Society, 182nd AAS Meeting, #77.07; Bulletin of the American Astronomical Society, Vol. 25, p.928
Astronomy and Astrophysics
Astronomy
Scientific paper
While COBE's detection of large-angle microwave background anisotropy fixes the amplitude of density fluctuations on length scales k(-1) ~ (300-6000) h(-1Mpc) , the quantity that determines the level of large-scale clustering is the amplitude of fluctuations on scales (5-50) h(-1Mpc) . The amount of dynamical clustering is parameterized by sigma_8 , the rms amplitude of the linear mass fluctuations in 8 h(-1Mpc) spheres. For the standard Cold Dark Matter model, the COBE result indicates sigma_8 ~ 1, while models with extra large scale power require sigma_8 ~ 1/2. The most massive clusters of galaxies (M gta 8 times 10(14) M_&sun;, sigma_v gta 700 km\ s(-1) ) form in rare `peak patches' found in the initial mass density distribution. The massive cluster abundance as a function of redshift is a sensitive probe of the wavenumber band k(-1) ~ (3-8) h(-1Mpc) , hence of sigma_8 , and so cluster evolution can discriminate among models allowed by the COBE results. We use our Hierarchical Peaks Method, which accurately reproduces the results of P(3M) N-body simulations, to calculate the evolution of cluster X-ray flux counts, luminosity and temperature functions as a function of sigma_8 for CDM models and those with more large scale power. We find that the EMSS and Edge et al. cluster samples support sigma_8 in the range from ~ 0.6-0.9, and that models with more large scale power (and hence flatter fluctuation spectra in the cluster regime) fit the X-ray bright end better. Uncertainties, pitfalls, and limitations of the method are discussed. Implications for X-Ray cluster samples and predictions for observations of the Sunyaev-Zeldovich effect are given.
Bond Richard J.
Myers Steven T.
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