Age-dating Luminous Red Galaxies observed with the Southern African
  Large Telescope
  We measure a value for the cosmic expansion of $H(z) = 89 \pm 23$(stat) $\pm$
44(syst) km s$^{-1}$ Mpc$^{-1}$ at a redshift of $z \simeq 0.47$ based on the
differential age technique. This technique, also known as cosmic chronometers,
uses the age difference between two redshifts for a passively evolving
population of galaxies to calculate the expansion rate of the Universe. Our
measurement is based on analysis of high quality spectra of Luminous Red
Galaxies (LRGs) obtained with the Southern African Large Telescope (SALT) in
two narrow redshift ranges of $z \simeq 0.40$ and $z \simeq 0.55$ as part of an
initial pilot study. Ages were estimated by fitting single stellar population
models to the observed spectra. This measurement presents one of the best
estimates of $H(z)$ via this method at $z\sim0.5$ to date.
