2000MNRAS.317..893L

New limits on the cosmic equation of state are derived from age measurements of three recently reported old high-redshift galaxies (OHRG). The results are based on a flat Friedmann-Robertson-Walker (FRW) type cosmological model driven by non-relativistic matter plus a smooth component parametrized by its equation of state p_xωρ_x (ω≥-1). The range of ω is strongly dependent on the matter density parameter. For Ω_M∼0.3, as indicated from dynamical measurements, the age estimates of the OHRG restrict the cosmic parameter to ω≤-0.27. However, if Ω_M is the one suggested by some studies of field galaxies, i.e., Ω_M≃0.5, only a cosmological constant (ω=-1) may be compatible with these data.