Dark Energy Survey Year 1 Results: redshift distributions of the weak-lensing source galaxies. Issue 1 (18th April 2018)

• Record Type: Journal Article
• Authors: Hoyle, B; Gruen, D; Bernstein, G M; Rau, M M; De Vicente, J; Hartley, W G; Gaztanaga, E; DeRose, J; Troxel, M A; Davis, C; Alarcon, A; MacCrann, N; Prat, J; Sánchez, C; Sheldon, E; Wechsler, R H; Asorey, J; Becker, M R; Bonnett, C; Rosell, A Carnero; Carollo, D; Kind, M Carrasco; Castander, F J; Cawthon, R; Chang, C; Childress, M; Davis, T M; Drlica-Wagner, A; Gatti, M; Glazebrook, K; Gschwend, J; Hinton, S R; Hoormann, J K; Kim, A G; King, A; Kuehn, K; Lewis, G; Lidman, C; Lin, H; Macaulay, E; Maia, M A G; Martini, P; Mudd, D; Möller, A; Nichol, R C; Ogando, R L C; Rollins, R P; Roodman, A; Ross, A J; Rozo, E; Rykoff, E S; Samuroff, S; Sevilla-Noarbe, I; Sharp, R; Sommer, N E; Tucker, B E; Uddin, S A; Varga, T N; Vielzeuf, P; Yuan, F; Zhang, B; Abbott, T M C; Abdalla, F B; Allam, S; Annis, J; Bechtol, K; Benoit-Lévy, A; Bertin, E; Brooks, D; Buckley-Geer, E; Burke, D L; Busha, M T; Capozzi, D; Carretero, J; Crocce, M; D'Andrea, C B; da Costa, L N; DePoy, D L; Desai, S; Diehl, H T; Doel, P; Eifler, T F; Estrada, J; Evrard, A E; Fernandez, E; Flaugher, B; Fosalba, P; Frieman, J; García-Bellido, J; Gerdes, D W; Giannantonio, T; Goldstein, D A; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Jarvis, M; Jeltema, T; Johnson, M W G; Johnson, M D; Kirk, D; Krause, E; Kuhlmann, S; Kuropatkin, N; Lahav, O; Li, T S; Lima, M; March, M; Marshall, J L; Melchior, P; Menanteau, F; Miquel, R; Nord, B; O'Neill, C R; Plazas, A A; Romer, A K; Sako, M; Sanchez, E; Santiago, B; Scarpine, V; Schindler, R; Schubnell, M; Smith, M; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Swanson, M E C; Tarle, G; Thomas, D; Tucker, D L; Vikram, V; Walker, A R; Weller, J; Wester, W; Wolf, R C; Yanny, B; Zuntz, J;
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 478:Issue 1(2018)
• Page Start: 592
• Page End: 610
• Publication Date: 2018-04-18
• Subjects: methods: data analysis -- catalogues -- surveys; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/sty957
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: We describe the derivation and validation of redshift distribution estimates and their uncertainties for the populations of galaxies used as weak-lensing sources in the Dark Energy Survey (DES) Year 1 cosmological analyses. The Bayesian Photometric Redshift (bpz ) code is used to assign galaxies to four redshift bins between z ≈ 0.2 and ≈1.3, and to produce initial estimates of the lensing-weighted redshift distributions $n^i_{\rm PZ}(z)\propto \mathrm{d}n^i/\mathrm{d}z$ for members of bin i . Accurate determination of cosmological parameters depends critically on knowledge of n i, but is insensitive to bin assignments or redshift errors for individual galaxies. The cosmological analyses allow for shifts $n^i(z)=n^i_{\rm PZ}(z-\Delta z^i)$ to correct the mean redshift of n i ( z ) for biases in $n^i_{\rm PZ}$ . The Δ z i are constrained by comparison of independently estimated 30-band photometric redshifts of galaxies in the Cosmic Evolution Survey (COSMOS) field to bpz estimates made from the DES griz fluxes, for a sample matched in fluxes, pre-seeing size, and lensing weight to the DES weak-lensing sources. In companion papers, the Δ z i of the three lowest redshift bins are further constrained by the angular clustering of the source galaxies around red galaxies with secure photometric redshifts at 0.15 < z < 0.9. This paper details the bpz and COSMOS procedures, and demonstrates that the cosmological inference is insensitive to details of the n i ( z ) beyond the choice of Δ z i . The clustering and COSMOS validation methods produce consistent estimates of Δ z i in the bins where both can be applied, with combined uncertainties of $\sigma_{\Delta z^i}=0.015, 0.013, 0.011, $ and 0.022 in the four bins. Repeating the photo- z procedure instead using the Directional Neighbourhood Fitting algorithm, or using the n i ( z ) estimated from the matched sample in COSMOS, yields no discernible difference in cosmological inferences.