Luminous Red Galaxies in Simulations: Cosmic Chronometers?

Understand

There have been a number of attempts to measure the expansion rate of the universe at high redshift using Luminous Red Galaxies (LRGs) as "chronometers".

• The method generally assumes that stars in LRGs are all formed at the same time.
• In this paper, we quantify the uncertainties on the measurement of H(z) which arise when one considers more realistic, extended star formation histories.
• In selecting galaxies from the Millennium Simulation for this study, we show that using rest-frame criteria significantly improves the homogeneity of the sample and that H(z) can be recovered to within 3% at z~0.42 even when extended star formation histories are considered.