Astronomy and Astrophysics – Astronomy
Scientific paper
May 1991
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1991tpsu.rept...31h&link_type=abstract
In MPI für Physik und Astrophysik, Traces of the Primordial Structure in the Universe p 31-37 (SEE N92-29833 20-90)
Astronomy and Astrophysics
Astronomy
Black Holes (Astronomy), Density Distribution, Flow Distribution, Galaxies, Velocity Distribution, Dark Matter, Galactic Evolution, Galactic Structure
Scientific paper
A method which uses the flow of galaxies from all directions into the Great Attractor as a simple but powerful test for the spectrum of density fluctuations and the value of the density parameter, is discussed. The most straightforward interpretation of the depth of the potential well at the Great Attractor is that the density parameter is rather high, and there is some strong observational evidence supporting the theoretical prejudice that the density parameter equals 1. This test is particularly effective because it probes the regime in which the perturbations are still linear, very few assumptions are required, and there are few of the uncertainties which beset other tests. Provided only that the perturbations are gravitational and Gaussian, and that galaxies trace the velocity field, the depth of the potential at the Great Attractor, plus the degree of nonlinearity of the density field, can be used to put tight constraints on models of galaxy formation. For example, limiting the nonlinearity of the density field by current microwave background limits constrains the density parameter to be approximately greater than 0.5 for cold dark matter models. Using the Infrared Astronomy Satellite (IRAS) density field to fix the level of nonlinearity as well argues that, on large scales, IRAS galaxies trace the mass density. Consideration of a wider range of power law fluctuation spectra allows the density parameter to be reduced to around 0.2 to 0.3, but values as low as required by nucleosynthesis for a baryonic Universe are strongly excluded.
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