1999ApJ...521L..87A

The ages of two old galaxies (53W091, 53W069) at high redshifts are used to constrain the value of the cosmological constant in a flat universe (ΛCDM) and the density parameter Ω_M in Friedmann-Robertson-Walker models with no Λ term. In the case of ΛCDM models, the quoted galaxies yield two lower limits for the vacuum energy density parameter, Ω_Λ≥0.42 and Ω_Λ≥0.5, respectively. Although compatible with the limits from statistics of gravitational lensing and cosmic microwave background, these lower bounds are more stringent than the ones recently determined using Type Ia supernovae as standard candles. For matter-dominated universes (Ω_Λ=0), the existence of these galaxies imply that the universe is open with the matter density parameter constrained by Ω_M≤0.45 and Ω_M≤0.37, respectively. In particular, these results disagree completely with the analysis of field galaxies, which gives a lower limit Ω_M≥0.40.