Quantifying the large-scale structure in the universe using rich galaxy clusters

Details Quantifying the large-scale structure in the universe using rich galaxy clusters Quantifying the large-scale structure in the universe using rich galaxy clusters

Nov 2000

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2000phdt........16m&link_type=abstract

Thesis (PhD). UNIVERSITY OF MAINE, Source DAI-B 61/05, p. 2577, Nov 2000, 180 pages.

Computer Science

1

Scientific paper

Galaxy clusters act as excellent mass tracers in our local Universe. They are bright, contain hundreds of galaxies, and are easy to observe. The most recognized galaxy cluster catalogs are those of Abell (1958) and Abell, Corwin and Olowin (1989-ACO). I present the results of a new survey of Abell/ACO cluster redshifts that extends our knowledge of the large-scale mass distribution in the Universe to a redshift of z = 0.14. The volume of the Universe traced by this survey is four times larger than any of its predecessors. The large number of clusters within the survey boundaries (606) as well as the large volume traced (~1.2 × 108h-3 Mpc3), allow for statistical analyses on scales never before probed. After discussing our data collection/analysis techniques, we create five subsets of Abell/ACO clusters. We use these samples to measure three spatial descriptors: the number density, the two-point spatial correlation function, and the power spectrum of density fluctuations. We find the number density of these rich clusters to be ~8.5 × 10-6h 3Mpc-3 out to z = 0.10. The two-point function, ξ(r), measures the relative numbers of cluster-cluster pairs, as compared to a random distribution, for a scale size r. The two-point function has the form ξ( r) = (r/ro)γ , where r is the separation length between clusters. All samples examined have 18.7 <= r0 <= 22.5( h-1Mpc) and -2.00 <= γ <= -1.85. These results are consistent with previous studies of the Abell catalog which provide evidence that the Universe is inhomogeneous to scales of at least 50-100h-1Mpc. The power spectrum, P(k), measures directly the fractional density enhancements, where the wavenumber k = 2π/λ, and λ specifies the size of the density fluctuations. Our largest sample of 606 clusters has a large volume that allows us to calculate P(k) to scales approaching 103h-1Mpc. We find that P(k) is a power-law on scales 0.02 <= k <= 0.10hMpc-1. Onlog-scales, we detect a flattening in the shape of P(k) from k = 0.02hMpc-1 down to the largest scales we can probe, k = 0.009hMpc -1, indicating that the Universe is homogeneous on scales ~300h -1Mpc. We compare the shape of the Abell/ACO rich cluster power spectrum to linear models and find that our results match closely to Open CDM and ACDM model Universes.

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