Title: "Photometric Redshifts and Dark Energy"

Abstract:

Upcoming wide area dark energy surveys (eg. DES, SNAP, LSST) will attempt to constrain dark energy parameters (Omega_DE, w_0, w_a) through a variety of complementary techniques such as galaxy cluster number statistics, weak lensing, galaxy angular correlations, and type Ia supernova. Having reliable photometric redshift is crucial to those methods because spectroscopic redshifts become prohibitively expensive for large scale surveys. Since uncertainty in the photometric redshift systematics is one of dominant sources of degradation of the Dark Energy constraints, we must fully understand photometric redshifts properties. In this poster, we present the results of our work in analyzing photo-z's, photo-z errors, and overall redshift and photo-z error distributions using the Dark Energy Survey (DES) simulations. The DES is a 5000 sq. deg. griz imaging survey to be conducted using a proposed 3 sq. deg. wide-field mosaic camera on the CTIO Blanco 4m telescope. We give a brief overview of the best photo-z and photo-z error methods, as well as the requirements imposed by the various scientific techniques. We show that the DES photometric redshifts will be accurate to sigma = 0.1 for z < 2 and the photometric redshift errors will be well behaved. The photo-z error requirements from the science techniques will be satisfied given our photo-z results and the proposed DES spectroscopic training galaxy sample. We discuss prospects for improvement.