Dark Energy

Participating Researchers: Kurt van der Heyden, Sarah Blyth
Current Postdoctoral Fellows: Mathew Smith
Current PhD students: Patrice Okouma

The nature of Dark Energy is one the great unknowns in modern Astrophysics/physics. We are interested in techniques to constrain the equation of state (w). Our group at UCT is particularly interested in using the type Ia supernovae (SNe) distance-luminosity relation as a probe of the nature of Dark Energy. Members of our group are also participants in the Sloan Supernova Survey (SDSS-SN), a large international collaboration dedicated to searching for SNe in the intermediate redshift range. Another promising method of constraining dark energy is the method of age-dating luminous red galaxies (LRGs). Typically LRGs are very massive, passive ellipticals situated in clusters. The key idea of this method is that the difference in cosmic age between two nearby redshifts is determined completely by the Hubble expansion rate at that redshift. Hence, if we know the age difference we know the Hubble constant at a particular redshift. The SCALPEL (SALT Cosmic Ages of Luminous Passive ELlipticals) project is mainly a South African collaboration aiming at measuring the expansion rate of the universe during various epochs in the past using LRGs. SCALPEL aims to obtain another high quality measurements of the Hubble Constant at higher redshifts (z>0.3). This will be valuable in further constraining current cosmological models and in particular shed some light on the behaviour of dark. The RSS (Robert Stobie Spectograph) on SALT (Souther African Large Telescope) will prove invaluable in obtaining spectra of sufficient quality for the purpose of age dating LRGs.