4 p.m. - 5 p.m. Location: SLC 2.303
Dr. Robert Kehoe (Southern Methodist University)
The study of the origin and evolution of the Universe has been a struggle to measure distance scales in the vastness of the cosmos. The determination of the true distances to galaxies and their consistent recession from us was enabled by the pioneering work on variable stars as standard candles. Decades of conflicting evidence and conclusions about Big Bang cosmology were apparently resolved by the more recent results from supernovae over a wide range of distances. These results suggest a flat universe which is however expanding at an ever accelerating rate. Questions remain about systematic effects from supernovae and about what transpires in the early, and more distant, universe when dark energy was not dominant. Several approaches have been pursued to test these results and to extend the reach to a much wider range of distances. The use of the evidence of acoustic oscillations observed in ‘visible’ (baryonic) matter distributions has proven to be a very valuable technique. A powerful new instrument, the Dark Energy Spectroscopic Instrument (DESI), is currently being developed to measure over 30 million galaxies over a broad range of distances. DESI constitutes a transformation of the Mayall 4m telescope at Kitt Peak National Observatory capable of simultaneously capturing 5000 spectra per exposure. Using baryon acoustic oscillation measurements, it will provide unprecedented precision on several cosmological properties. Among these, a detailed history of the expansion of the universe is expected. Kehoe will present some recent results which comment on our knowledge of the cosmic distance ladder. His main focus will be on the use of acoustic oscillation measurements, and the motivation and plans for DESI. Anticipated results will also be reviewed.