Dr. Martin Hendry
U. Glasgow

University of Florida Astronomy Colloquium - Oct. 22, 2008

Galaxy distance indicators: past, present and future

The study of the cosmic distance scale has a long and illustrious history in astronomy, stretching back to the pioneering work of Edwin Hubble himself. Within the past 15 years observations with the Hubble Space Telescope have greatly improved our calibration of the distance scale, largely removing the factor of two uncertainty in the expansion rate of the Universe which previously dogged cosmology for decades. Meanwhile the focus of attention has switched to cosmological distance indicators at higher redshift, and their use in constraining the nature and distribution of dark energy. Despite entering this new and exciting phase, however, many of the classic statistical issues that fuelled the old "factor of two" controversy are still present, and their impact on the calibration and use of high-redshift distance indicators is now an important topic.

In this talk I will review recent progress on mapping the cosmic distance scale, and its implications for constraining cosmological models. After focussing on "traditional" distance indicators, such as Cepheids and supernovae, I will then discuss the future prospects for extending the extragalactic distance scale to much higher redshift using gravitational wave observations of binary black hole mergers - so called "standard sirens". I will illustrate some cosmological questions that might be addressed with future siren observations, as well as highlighting the potential systematic errors to which they are vulnerable, and which must be overcome if they are to be fully exploited as cosmological probes.