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The Buzzard Flock: Dark Energy Survey Synthetic Sky Catalogs

Joseph DeRose, Risa H. Wechsler, Matthew R. Becker, Michael T. Busha, Eli S. Rykoff, Niall MacCrann, Brandon Erickson, August E. Evrard, Andrey Kravtsov, Daniel Gruen, Sahar Allam, Santiago Avila, Sarah Bridle, David Brooks, Elizabeth Buckley-Geer, Aurelio Carnero Rosell, Matias Carrasco Kind, Jorge Carretero, Francisco J. Castander, Ross Cawthon, Martin Crocce, Luiz N. da Costa, Christopher Davis, Juan De Vicente, Jörg P. Dietrich, Peter Doel, Alex Drlica-Wagner, Pablo Fosalba, Josh Frieman, Juan Garcia-Bellido, Gaston Gutierrez, Will G. Hartley, Devon L. Hollowood, Ben Hoyle, David J. James, Elisabeth Krause, Kyler Kuehn, Nikolay Kuropatkin, Marcos Lima, Marcio A. G. Maia, Felipe Menanteau, Christopher J. Miller, Ramon Miquel, Ricardo L. C. Ogando, Andrés Plazas Malagón, A. Kathy Romer, Eusebio Sanchez, Rafe Schindler, Santiago Serrano, Ignacio Sevilla-Noarbe, Mathew Smith, Eric Suchyta, Molly E. C. Swanson, Gregory Tarle, Vinu Vikram

TL;DR

The paper addresses the need for realistic, multi-probe mocks to study systematics in DES Y1 analyses. It presents the Buzzard suite of 18 synthetic sky catalogs produced with ADDGALS embedded in light-cone N-body simulations, with full ray-traced lensing and a common LCDM cosmology, yielding ~820 million galaxies over 1120 deg^2. The mocks reproduce observed distributions of magnitudes, colors, redshifts, and mass–observable relations, and provide publicly available data vectors for DES cosmology studies, enabling robust testing of pipelines and cluster finding. This scalable, computationally efficient framework supports covariance estimation and QA across galaxy clustering, weak lensing, and cluster analyses, and is adaptable to future surveys beyond DES.

Abstract

We present a suite of 18 synthetic sky catalogs designed to support science analysis of galaxies in the Dark Energy Survey Year 1 (DES Y1) data. For each catalog, we use a computationally efficient empirical approach, ADDGALS, to embed galaxies within light-cone outputs of three dark matter simulations that resolve halos with masses above ~5x10^12 h^-1 m_sun at z <= 0.32 and 10^13 h^-1 m_sun at z~2. The embedding method is tuned to match the observed evolution of galaxy counts at different luminosities as well as the spatial clustering of the galaxy population. Galaxies are lensed by matter along the line of sight --- including magnification, shear, and multiple images --- using CALCLENS, an algorithm that calculates shear with 0.42 arcmin resolution at galaxy positions in the full catalog. The catalogs presented here, each with the same LCDM cosmology (denoted Buzzard), contain on average 820 million galaxies over an area of 1120 square degrees with positions, magnitudes, shapes, photometric errors, and photometric redshift estimates. We show that the weak-lensing shear catalog, redMaGiC galaxy catalogs and redMaPPer cluster catalogs provide plausible realizations of the same catalogs in the DES Y1 data by comparing their magnitude, color and redshift distributions, angular clustering, and mass-observable relations, making them useful for testing analyses that use these samples. We make public the galaxy samples appropriate for the DES Y1 data, as well as the data vectors used for cosmology analyses on these simulations.

The Buzzard Flock: Dark Energy Survey Synthetic Sky Catalogs

TL;DR

The paper addresses the need for realistic, multi-probe mocks to study systematics in DES Y1 analyses. It presents the Buzzard suite of 18 synthetic sky catalogs produced with ADDGALS embedded in light-cone N-body simulations, with full ray-traced lensing and a common LCDM cosmology, yielding ~820 million galaxies over 1120 deg^2. The mocks reproduce observed distributions of magnitudes, colors, redshifts, and mass–observable relations, and provide publicly available data vectors for DES cosmology studies, enabling robust testing of pipelines and cluster finding. This scalable, computationally efficient framework supports covariance estimation and QA across galaxy clustering, weak lensing, and cluster analyses, and is adaptable to future surveys beyond DES.

Abstract

We present a suite of 18 synthetic sky catalogs designed to support science analysis of galaxies in the Dark Energy Survey Year 1 (DES Y1) data. For each catalog, we use a computationally efficient empirical approach, ADDGALS, to embed galaxies within light-cone outputs of three dark matter simulations that resolve halos with masses above ~5x10^12 h^-1 m_sun at z <= 0.32 and 10^13 h^-1 m_sun at z~2. The embedding method is tuned to match the observed evolution of galaxy counts at different luminosities as well as the spatial clustering of the galaxy population. Galaxies are lensed by matter along the line of sight --- including magnification, shear, and multiple images --- using CALCLENS, an algorithm that calculates shear with 0.42 arcmin resolution at galaxy positions in the full catalog. The catalogs presented here, each with the same LCDM cosmology (denoted Buzzard), contain on average 820 million galaxies over an area of 1120 square degrees with positions, magnitudes, shapes, photometric errors, and photometric redshift estimates. We show that the weak-lensing shear catalog, redMaGiC galaxy catalogs and redMaPPer cluster catalogs provide plausible realizations of the same catalogs in the DES Y1 data by comparing their magnitude, color and redshift distributions, angular clustering, and mass-observable relations, making them useful for testing analyses that use these samples. We make public the galaxy samples appropriate for the DES Y1 data, as well as the data vectors used for cosmology analyses on these simulations.

Paper Structure

This paper contains 6 sections, 7 equations, 1 figure.

Table of Contents

  1. Introduction
  2. Simulation Requirements
  3. Galaxy Clustering
  4. Galaxy Lensing
  5. Cluster Counts
  6. Creating Synthetic Dark Energy Surveys

Figures (1)

  • Figure 1: A synthetic Dark Energy Survey sky. Top: Projected matter density field of one Buzzard footprint, corresponding to the SPT area of the DES Y1 footprint, with $>50$ redMaPPer clusters plotted as the black circles. Many analyses have used only the portion of this footprint with $\textrm{RA}<300$. Bottom: Zoom in of a massive halo. The color map represents matter density and black whiskers are the direction and amplitude of the true shear of background galaxies in our simulated Y1 weak-lensing catalogs.