Dark energy and the epoch of galaxy formation

The influence of a dark component on the first epoch of galaxy formation is analyzed by using the ages of the three oldest high-redshift galaxies know n in the literature. Our results, based on a spatially flat accelerated uni verse driven by a "quintessence" component (p(x) = omega rho (x)), show tha t, if the inferred ages of these objects are correct, the first formation e ra is pushed back to extremely high redshifts. For the present best- fit qu intessence model (Omegax = 0.7, omega < -0.6), we find a lower bound of z(f ) <greater than or equal to> 7.7, whereas in the extreme case of the Lambda + cold dark matter model (omega = -1) the limit is slightly smaller (z(f) greater than or equal to 5.8). The case for open cold dark matter models ha s also been discussed. For Omega (m) similar or equal to 0.3, the formation redshift is restricted by zf greater than or equal to 18. As a general res ult, if Omega (m) greater than or equal to 0.37, these galaxies are not for med in FRW cosmologies with no dark energy since for all these cases z(f) - -> infinity.