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The Mass Density of the Universe

Published online by Cambridge University Press:  26 May 2016

Neta A. Bahcall
Neta A. Bahcall*
Affiliation:
Princeton University Observatory, Astrophysical Sciences Department, Peyton Hall, Princeton, NJ 08544-1001, USA

Abstract

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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.

Type
Part VIII: Dark Matter and Ω0
Information
Symposium - International Astronomical Union , Volume 201: New Cosmological Data and the Values of the Fundamental Parameters , 2005 , pp. 322 - 329
Copyright
Copyright © Astronomical Society of the Pacific 2005 

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