Photometric Redshifts for the Dark Energy Survey

Details Photometric Redshifts for the Dark Energy Survey Photometric Redshifts for the Dark Energy Survey

Jun 2006

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006aas...208.6003o&link_type=abstract

American Astronomical Society Meeting 208, #60.03; Bulletin of the American Astronomical Society, Vol. 38, p.140

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Scientific paper

The Dark Energy Survey (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. The primary scientific goal of the DES is to constrain dark energy cosmological parameters via 4 complementary methods: galaxy clusters, weak lensing, galaxy angular correlations, and Type Ia supernovae. Crucial to DES science is the measurement of well-understood photometric redshifts and errors, derived from the survey griz imaging, for both cluster and field galaxies alike. Here we present the photometric redshifts calculated for galaxies in the DES Level 1 Catalog Simulations (CatSim1), which is based on a parent Hubble Volume N-body simulation combined with an algorithm that assigns mock galaxies which reproduce the observed luminosity-color-density correlations from the SDSS. We show comparisons of different photometric redshift techniques, specifically template fitting, nearest neighbor polynomial fitting, and neural networks. In addition, we show results of the nearest neighbor error estimator (NNE) applied to neural-network photometric redshifts, as well as the shape of the resulting error distribution. Using the error estimates from NNE to remove catastrophic objects we find that the DES will obtain photometric redshifts with an error σ = 0.1 for its overall galaxy sample. Finally, we examine the benefits of adding complementary near-IR imaging data, specifically from VISTA, showing that the combination of optical plus near-IR data significantly reduces the photo-z bias and the photo-z scatter, down to σ = 0.07 for the overall DES galaxy sample.

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