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Dark Energy Survey Year 1 Results: Weak Lensing Shape Catalogues

J. Zuntz, E. Sheldon, S. Samuroff, M. A. Troxel, M. Jarvis, N. MacCrann, D. Gruen, J. Prat, C. Sánchez, A. Choi, S. L. Bridle, G. M. Bernstein, S. Dodelson, A. Drlica-Wagner, Y. Fang, R. A. Gruendl, B. Hoyle, E. M. Huff, B. Jain, D. Kirk, T. Kacprzak, C. Krawiec, A. A. Plazas, R. P. Rollins, E. S. Rykoff, I. Sevilla-Noarbe, B. Soergel, T. N. Varga, T. M. C. Abbott, F. B. Abdalla, S. Allam, J. Annis, K. Bechtol, A. Benoit-Lévy, E. Bertin, E. Buckley-Geer, D. L. Burke, A. Carnero Rosell, M. Carrasco Kind, J. Carretero, F. J. Castander, M. Crocce, C. E. Cunha, C. B. D'Andrea, L. N. da Costa, C. Davis, S. Desai, H. T. Diehl, J. P. Dietrich, P. Doel, T. F. Eifler, J. Estrada, A. E. Evrard, A. Fausti Neto, E. Fernandez, B. Flaugher, P. Fosalba, J. Frieman, J. García-Bellido, E. Gaztanaga, D. W. Gerdes, T. Giannantonio, J. Gschwend, G. Gutierrez, W. G. Hartley, K. Honscheid, D. J. James, T. Jeltema, M. W. G. Johnson, M. D. Johnson, K. Kuehn, S. Kuhlmann, N. Kuropatkin, O. Lahav, T. S. Li, M. Lima, M. A. G. Maia, M. March, P. Martini, P. Melchior, F. Menanteau, C. J. Miller, R. Miquel, J. J. Mohr, E. Neilsen, R. C. Nichol, R. L. C. Ogando, N. Roe, A. K. Romer, A. Roodman, E. Sanchez, V. Scarpine, R. Schindler, M. Schubnell, M. Smith, R. C. Smith, M. Soares-Santos, F. Sobreira, E. Suchyta, M. E. C. Swanson, G. Tarle, D. Thomas, D. L. Tucker, V. Vikram, A. R. Walker, R. H. Wechsler, Y. Zhang

TL;DR

DES Year 1 delivers two independent weak-lensing shape catalogues, METACALIBRATION and IM3SHAPE, spanning 1500 deg^2 with median redshift ~0.59 and enabling robust cosmic shear and galaxy-galaxy lensing analyses. METACALIBRATION calibrates shear via per-object responses derived directly from data, while IM3SHAPE relies on image-simulation calibrations (Hoopoe) to correct model/noise biases; both catalogs undergo comprehensive PSF, blending, and null tests, yielding 1σ multiplicative biases of approximately 0.013 and 0.025, respectively. The paper details data processing, PSF handling, blending treatments, and extensive validation tests (including B-modes and PSF leakage), and provides a structured error budget and guidance for usage, including tomographic robustness considerations. These results demonstrate the viability of the DES Y1 data for precision weak-lensing science and establish a framework for future multi-year, multi-band calibrations and method cross-checks, with plans to adopt advanced techniques like BFD and enhanced PSF pipelines in upcoming analyses.

Abstract

We present two galaxy shape catalogues from the Dark Energy Survey Year 1 data set, covering 1500 square degrees with a median redshift of $0.59$. The catalogues cover two main fields: Stripe 82, and an area overlapping the South Pole Telescope survey region. We describe our data analysis process and in particular our shape measurement using two independent shear measurement pipelines, METACALIBRATION and IM3SHAPE. The METACALIBRATION catalogue uses a Gaussian model with an innovative internal calibration scheme, and was applied to $riz$-bands, yielding 34.8M objects. The IM3SHAPE catalogue uses a maximum-likelihood bulge/disc model calibrated using simulations, and was applied to $r$-band data, yielding 21.9M objects. Both catalogues pass a suite of null tests that demonstrate their fitness for use in weak lensing science. We estimate the 1$σ$ uncertainties in multiplicative shear calibration to be $0.013$ and $0.025$ for the METACALIBRATION and IM3SHAPE catalogues, respectively.

Dark Energy Survey Year 1 Results: Weak Lensing Shape Catalogues

TL;DR

DES Year 1 delivers two independent weak-lensing shape catalogues, METACALIBRATION and IM3SHAPE, spanning 1500 deg^2 with median redshift ~0.59 and enabling robust cosmic shear and galaxy-galaxy lensing analyses. METACALIBRATION calibrates shear via per-object responses derived directly from data, while IM3SHAPE relies on image-simulation calibrations (Hoopoe) to correct model/noise biases; both catalogs undergo comprehensive PSF, blending, and null tests, yielding 1σ multiplicative biases of approximately 0.013 and 0.025, respectively. The paper details data processing, PSF handling, blending treatments, and extensive validation tests (including B-modes and PSF leakage), and provides a structured error budget and guidance for usage, including tomographic robustness considerations. These results demonstrate the viability of the DES Y1 data for precision weak-lensing science and establish a framework for future multi-year, multi-band calibrations and method cross-checks, with plans to adopt advanced techniques like BFD and enhanced PSF pipelines in upcoming analyses.

Abstract

We present two galaxy shape catalogues from the Dark Energy Survey Year 1 data set, covering 1500 square degrees with a median redshift of . The catalogues cover two main fields: Stripe 82, and an area overlapping the South Pole Telescope survey region. We describe our data analysis process and in particular our shape measurement using two independent shear measurement pipelines, METACALIBRATION and IM3SHAPE. The METACALIBRATION catalogue uses a Gaussian model with an innovative internal calibration scheme, and was applied to -bands, yielding 34.8M objects. The IM3SHAPE catalogue uses a maximum-likelihood bulge/disc model calibrated using simulations, and was applied to -band data, yielding 21.9M objects. Both catalogues pass a suite of null tests that demonstrate their fitness for use in weak lensing science. We estimate the 1 uncertainties in multiplicative shear calibration to be and for the METACALIBRATION and IM3SHAPE catalogues, respectively.

Paper Structure

This paper contains 65 sections, 28 equations, 30 figures, 10 tables.

Table of Contents

  1. Introduction
  2. Data
  3. Observing Period and Conditions
  4. Object Catalogue
  5. Galaxy Selection
  6. Astrometry
  7. COSMOS Data
  8. Blinding
  9. PSF Estimation
  10. Selection of PSF Stars
  11. PSF Measurement and Interpolation
  12. PSF Model Diagnostics
  13. The metacalibration Catalogue
  14. metacalibration Overview
  15. metacalibration in DES Y1
  16. ...and 50 more sections

Figures (30)

  • Figure 1: A flow-chart showing the steps in the DES Year 1 shape analysis, starting from low-level calibrated data products made by DES Data Management (DES-DM) and ending with final output catalogues. Yellow stages are performed in the DES-DM software process. Green stages are performed in the Weak Lensing analysis process. Blue stages are part of the im3shape process, mostly simulation and calibration, and red stages part of the metacalibration analysis. "S.E." stands for "single epoch".
  • Figure 2: The DES Y1 shear catalogue footprint with galaxy density of the metacalibration catalogue shown with the nominal 5-year DES footprint outline overlayed. im3shape is qualitatively similar, but slightly shallower. We define three fields: 1) The large, southern field overlapping with SPT, which has been selected for DES Y1 science applications due to contiguity. 2) The long equatorial strip overlapping with SDSS Stripe 82. 3) The disjoint supernovae and spectroscopic-overlap fields, which have been selected from the 4 exposure depth (D04) Gold catalogue. Additional D04 fields far from the SPT region are not shown. The densities are not corrected for the detection fraction within each pixel. The Albers equal-area projection is used.
  • Figure 3: Magnitude histograms showing different selections of the DES Y1 catalogues. Values are measured with the multi-object fitting (MOF) method described in y1gold. The Gold catalogue is the input detection catalogue described in § \ref{['sec:gold']}. "Galaxies" are those identified as galaxies by the process described in § \ref{['sec:galaxy selection']}. "Good" galaxies are those with no indication of blending or extreme colours from SEx-tractor. The metacalibration and im3shape histograms show objects in the final shape catalogues, after method-specific cuts.
  • Figure 4: An example size-magnitude diagram for a single CCD image, used to identify stars.
  • Figure 5: The distribution of the numbers of stars used to constrain the PSF model per CCD image.
  • ...and 25 more figures