Supernovae as Probes of Dark Energy
The use of Type Ia supernovae as distance indicators led to the discovery of the accelerating expansion of the Universe more than a decade ago. Large 2nd generation surveys have significantly increased the size and quality of the high-redshift sample.
The critical low-redshift reference sample useful for cosmology remains small by comparison. The Nearby Supernova Factory (SNfactory) is using new nearby Type Ia supernovae to strengthen the measurement of the dark energy equation of state, with an emphasis on controlling systematic uncertainties and better understanding the underlying physics associated with Type Ia supernovae as distance indicators.
To meet these goals the SNfactory developed two new approaches to the problem -- an ultra-wide-field CCD survey to find supernovae irrespective of an associated host galaxy, and replacement of filter-based supernova lightcurves with full spectral time series. In this talk I will discuss recent progress in measuring the dark energy equation of state with both high- and low-redshift supernovae, focusing on results from the Nearby Supernova Factory. The role of the low redshift sample for upcoming high-redshift surveys, such as DES, LSST-SN and WFIRST, also will be discussed.