Angular Diameters as a Probe of a Cosmological Constant and $\Omega$

Abstract

The lensing effect of curved space, which can cause the angular diameter of a fixed reference length seen on the sky to reach a minimum and then increase with redshift, depends sensitively on the value of the cosmological constant, $\Lambda$, in a flat universe. The redshift of an observed minimum and the asymptotic slope can in principle provide strong constraints on $\Lambda$. The sensitivity to a non-zero cosmological constant in a flat universe is compared to the sensitivity to $q_0$ in an open universe without a cosmological constant, and to inherent ambiguities due to uncertainties in distance measures and the possible effects of evolution. If evolutionary uncertainties can be overcome, the reported observations of the angular diameter of compact radio jets as a function of redshift, which appear to exhibit such a minimum, could provide the strongest available limit on the cosmological constant in a flat universe, and on $\Omega$ in an open universe.

10 pages plus 4 figures (not included)

Cited by in corpus (16)

• Evolution of the Scale Factor with a Variable Cosmological Term
• The Cosmological Constant is Back
• Dark energy and the angular size - redshift diagram for milliarcsecond radio sources
• Constraining Omega_0 With The Angular-Size Redshift Relation Of Double-Lobed Quasars In The FIRST Survey
• A Low-Density Closed Universe
• Studying the decay of the vacuum energy with the observed density fluctuation spectrum
• One Hundred Years of the Cosmological Constant: from 'Superfluous Stunt' to Dark Energy
• The Hubble Diagram of Type Ia Supernovae in Non-Uniform Pressure Universes
• The angular size - redshift relation in power-law cosmologies
• Distances in inhomogeneous quintessence cosmology
• Decay of the vacuum energy into CMB photons
• The Maximum Angular-Diameter Distance in Cosmology
• The Angular-Diameter-Distance-Maximum and Its Redshift as Constraints on $\Lambda \ne 0$ FLRW Models
• Gravitational wave source counts at high redshift and in models with extra dimensions
• Minimal Angular Size of Distant Sources in Open, $\Lambda$CDM, and Scalar Field Cosmologies
• Flat Cosmology with Coupled Matter and Dark Energies