Observed Densities in the Universe |
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Authors: | Tammann G A |
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Institution: | (1) Astronomisches Institut der Universität Basel, Venusstr. 7, CH-4102 Binningen, Switzerland |
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Abstract: | Baryons observed in Ly absorbers contribute to the density parameter 0 by bar 0.06 in close agreement with the value of 0.06 from primordial nucleosynthesis (H0=55 km s-1 Mpc-1, = 0 assumed throughout). A number of methods are known to measure 0 from density fluctuations; bound structures tend to yield lower values ( m 0.2-0.4), field galaxies over large scales higher, but still undercritical values ( m 0.6 ± 0.2). The best compromise value is 0 0.5, but the present methods are blind to diffusely distributed, exotic matter which still could make 0 = 1. A satisfactory solution of 0 (and ) will only come from a fundamental cosmological test (e.g. the Hubble diagram of evolution-corrected] supernovae type Ia) in combination with the CMB fluctuation spectrum. |
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