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The Mass Density of the Universe
Published online by Cambridge University Press: 26 May 2016
Abstract
One of the most fundamental questions in cosmology is: How much matter is there in the Universe and how is it distributed? Here I show that several independent measures-including those utilizing clusters of galaxies-all indicate that the mass-density of the Universe is low-only ˜20% of the critical density. Recent measurements of the mass-to-light function-from galaxies, to groups, clusters, and superclusters-provide a powerful new measure of the universal density. The results reveal a low density of 0.16±0.05 the critical density. The observations suggest that, on average, the mass distribution follows the light distribution on large scales. The results, combined with the recent observations of high redshift supernovae and the spectrum of the CMB anisotropy, suggest a Universe that has low density (Ωm ⋍0.2), is flat, and is dominated by dark energy.
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- Part VIII: Dark Matter and Ω0
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- Copyright © Astronomical Society of the Pacific 2005