Current lookback time-redshift bounds on dark energy

We investigate observational constraints on dark energy models from lookback time (LT) estimates of 32 old passive galaxies distributed over the redshift interval 0.11⩽z⩽1.84. To build up our LT sample we combine the age measurements for these 32 objects with estimates of the total age of the Universe, as obtained from current CMB data. We show that LT data may provide bounds on the cosmological parameters with accuracy competitive with type Ia Supernova methods. In order to break possible degeneracies between models parameters, we also discuss the bounds when our lookback time versus redshift sample is combined with the recent measurement of the baryonic acoustic oscillation peak and the derived age of the Universe from current CMB measurements.