Year: 1994
Type: article
Abstract: We propose a method for deriving a dynamical lower bound on {OMEGA} from diverging flows in low-density regions, based on the fact that large outflows are not expected in a low-{OMEGA} universe. The velocities are assumed to be induced by gravity from small initial fluctuations, but no assumptions are made regarding galaxy biasing, the exact statistical nature of the fluctuations or {LAMBDA}. The derivatives of a diverging velocity field infer a nonlinear approximation to the mass density, which is an overestimate when the true value of {OMEGA} is assumed. This inferred density can become ridiculously negative when the assumed {OMEGA} is too low, thus bounding {OMEGA}. Observed radial peculiar velocities of galaxies allow the POTENT procedure to recover the required velocity field, Gaussian smoothed at 1200 km s^-1^. The density and the associated errors are then inferred for different values of {OMEGA}, searching for a void which shows negative inferred density with high confidence. A preliminary application to data in a southern void indicates that {OMEGA} <= 0.3 can be ruled out at the 2.4 σ level. A detailed study of possible systematic errors is under way.
Source: The Astrophysical Journal
DOI: 10.1086/187197
Authors: Avishai Dekel, Martin J. Rees
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2034101457