Dark Energy Survey Year 1 results: The impact of galaxy neighbours on weak lensing cosmology with IM3SHAPE

DES Collaboration

doi:10.1093/mnras/stx3282

Dark Energy Survey Year 1 results: The impact of galaxy neighbours on weak lensing cosmology with IM3SHAPE

DES Collaboration

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Abstract

We use a suite of simulated images based on Year 1 of the Dark Energy Survey to explore the impact of galaxy neighbours on shape measurement and shear cosmology. The HOOPOE image simulations include realistic blending, galaxy positions, and spatial variations in depth and point spread function properties. Using the IM3SHAPE maximum-likelihood shape measurement code, we identify four mechanisms by which neighbours can have a non-negligible influence on shear estimation. These effects, if ignored, would contribute a net multiplicative bias of m ~ 0.03-0.09 in the Year One of the Dark Energy Survey (DES Y1) IM3SHAPE catalogue, though the precise impact will be dependent on both the measurement code and the selection cuts applied. This can be reduced to percentage level or less by removing objects with close neighbours, at a cost to the effective number density of galaxies neff of 30 per cent. We use the cosmological inference pipeline of DES Y1 to explore the cosmological implications of neighbour bias and show that omitting blending from the calibration simulation for DES Y1 would bias the inferred clustering amplitude S₈ ≡ σ₈(Ω_m/0.3)^0.5 by 2σ towards low values. Finally, we use the HOOPOE simulations to test the effect of neighbour-induced spatial correlations in the multiplicative bias.We find the impact on the recovered S₈ of ignoring such correlations to be subdominant to statistical error at the current level of precision.

Original language	English
Pages (from-to)	4524-4543
Number of pages	20
Journal	Monthly Notices of the Royal Astronomical Society
Volume	475
Issue number	4
DOIs	https://doi.org/10.1093/mnras/stx3282
State	Published - Apr 21 2018

Funding

Based in part on observations at Cerro Tololo Inter-American Observatory, National Optical Astronomy Observatory, which is operated by the Association of Universities for Research in As- tronomy (AURA) under a cooperative agreement with the National Science Foundation. We thank Nicolas Tessore, Catherine Heymans, and Rachel Man-delbaum for various insights that contributed to this work. We are also indebted to the many DES ‘eyeballers’ for lending their holiday time to help us understand and validate our simulations. The HOOPOE simulations were generated using the National Energy Research Scientific Computing Center (NERSC) facility, which is maintained by the U.S. Department of Energy. The likelihood calculations were performed using NERSC and the Fornax computing cluster, which was funded by the European Research Council. SLB acknowledges support from the European Research Council in the form of a Consolidator Grant with number 681431. Support for DG was provided by NASA through Einstein Postdoctoral Fellowship grant number PF5-160138 awarded by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060. The DES data management system is supported by the National Science Foundation under Grant Numbers AST-1138766 and AST-1536171. The DES participants from Spanish institutions are partially supported by MINECO under grants AYA2015-71825, ESP2015-88861, FPA2015-68048, SEV-2012-0234, SEV-2016-0597, and MDM-2015-0509, some of which include ERDF funds from the European Union. IFAE is partially funded by the CERCA program of the Generalitat de Catalunya. Research leading to these results has received funding from the European Research Council under the European Union’s Seventh Framework Program (FP7/2007-2013) including ERC grant agreements 240672, 291329, and 306478. We acknowledge support from the Australian Research Council Centre of Excellence for All-sky Astrophysics (CAAS-TRO), through project number CE110001020. Funding for the DES Projects has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, the Center for Cosmology and Astro-Particle Physics at the Ohio State University, the Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University, Financiadora de Estudos e Projetos, Fundac¸ão Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desen-volvimento Científico e Tecnológico and the Ministério da Ciência, Tecnologia e Inovac¸ão, the Deutsche Forschungsgemeinschaft, and the Collaborating Institutions in the Dark Energy Survey. This manuscript has been authored by Fermi Research Alliance, LLC under Contract No. DE-AC02-07CH11359 with the U.S. Department of Energy, Office of Science, Office of High Energy Physics. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes.

Funders	Funder number
Australian Research Council Centre of Excellence for All-sky Astrophysics
CAAS-TRO	CE110001020
Collaborating Institutions in the Dark Energy Survey
Conselho Nacional de Desen-volvimento Científico e Tecnológico
European Union’s Seventh Framework Program
FP7/2007
Fermi Research Alliance, LLC	DE-AC02-07CH11359
Kavli Institute of Cosmological Physics at the University of Chicago
Ministry of Science and Education of Spain
Mitchell Institute for Fundamental Physics and Astronomy at Texas A&M University
National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign
U.S. National Science Foundation
National Science Foundation	AST-1138766, AST-1536171
U.S. Department of Energy
National Aeronautics and Space Administration	PF5-160138, NAS8-03060
Office of Science
High Energy Physics
Seventh Framework Programme	681431, 1138766, 240672, 306478, 291329
Higher Education Funding Council for England
Center for Cosmology and Astroparticle Physics, Ohio State University
Science and Technology Facilities Council
European Commission
European Research Council
Deutsche Forschungsgemeinschaft
Generalitat de Catalunya
Ministerio de Economía y Competitividad	ESP2015-88861, SEV-2016-0597, MDM-2015-0509, FPA2015-68048, SEV-2012-0234, AYA2015-71825
Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro
Financiadora de Estudos e Projetos
Ministério da Ciência e Tecnologia
European Regional Development Fund

Keywords

Cosmological parameters
Cosmology: observations
Galaxies: statistics
Gravitational lensing: weak

Access to Document

10.1093/mnras/stx3282

Cite this

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title = "Dark Energy Survey Year 1 results: The impact of galaxy neighbours on weak lensing cosmology with IM3SHAPE",

abstract = "We use a suite of simulated images based on Year 1 of the Dark Energy Survey to explore the impact of galaxy neighbours on shape measurement and shear cosmology. The HOOPOE image simulations include realistic blending, galaxy positions, and spatial variations in depth and point spread function properties. Using the IM3SHAPE maximum-likelihood shape measurement code, we identify four mechanisms by which neighbours can have a non-negligible influence on shear estimation. These effects, if ignored, would contribute a net multiplicative bias of m ~ 0.03-0.09 in the Year One of the Dark Energy Survey (DES Y1) IM3SHAPE catalogue, though the precise impact will be dependent on both the measurement code and the selection cuts applied. This can be reduced to percentage level or less by removing objects with close neighbours, at a cost to the effective number density of galaxies neff of 30 per cent. We use the cosmological inference pipeline of DES Y1 to explore the cosmological implications of neighbour bias and show that omitting blending from the calibration simulation for DES Y1 would bias the inferred clustering amplitude S8 ≡ σ8(Ωm/0.3)0.5 by 2σ towards low values. Finally, we use the HOOPOE simulations to test the effect of neighbour-induced spatial correlations in the multiplicative bias.We find the impact on the recovered S8 of ignoring such correlations to be subdominant to statistical error at the current level of precision.",

keywords = "Cosmological parameters, Cosmology: observations, Galaxies: statistics, Gravitational lensing: weak",

author = "{DES Collaboration} and S. Samuroff and Bridle, {S. L.} and J. Zuntz and Troxel, {M. A.} and D. Gruen and Rollins, {R. P.} and Bernstein, {G. M.} and Eifler, {T. F.} and Huff, {E. M.} and T. Kacprzak and E. Krause and N. MacCrann and Abdalla, {F. B.} and S. Allam and J. Annis and K. Bechtol and A. Benoit-L{\'e}vy and E. Bertin and D. Brooks and E. Buckley-Geer and {Carnero Rosell}, A. and {Carrasco Kind}, M. and J. Carretero and M. Crocce and D'Andrea, {C. B.} and {da Costa}, {L. N.} and C. Davis and S. Desai and P. Doel and {Fausti Neto}, A. and B. Flaugher and P. Fosalba and J. Frieman and J. Garc{\'i}a-Bellido and Gerdes, {D. W.} and Gruendl, {R. A.} and J. Gschwend and G. Gutierrez and K. Honscheid and James, {D. J.} and M. Jarvis and T. Jeltema and D. Kirk and K. Kuehn and S. Kuhlmann and Li, {T. S.} and M. Lima and Maia, {M. A.G.} and M. March and E. Suchyta",

note = "Publisher Copyright: {\textcopyright} 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.",

year = "2018",

month = apr,

day = "21",

doi = "10.1093/mnras/stx3282",

language = "English",

volume = "475",

pages = "4524--4543",

journal = "Monthly Notices of the Royal Astronomical Society",

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TY - JOUR

T1 - Dark Energy Survey Year 1 results

T2 - The impact of galaxy neighbours on weak lensing cosmology with IM3SHAPE

AU - DES Collaboration

AU - Samuroff, S.

AU - Bridle, S. L.

AU - Zuntz, J.

AU - Troxel, M. A.

AU - Gruen, D.

AU - Rollins, R. P.

AU - Bernstein, G. M.

AU - Eifler, T. F.

AU - Huff, E. M.

AU - Kacprzak, T.

AU - Krause, E.

AU - MacCrann, N.

AU - Abdalla, F. B.

AU - Allam, S.

AU - Annis, J.

AU - Bechtol, K.

AU - Benoit-Lévy, A.

AU - Bertin, E.

AU - Brooks, D.

AU - Buckley-Geer, E.

AU - Carnero Rosell, A.

AU - Carrasco Kind, M.

AU - Carretero, J.

AU - Crocce, M.

AU - D'Andrea, C. B.

AU - da Costa, L. N.

AU - Davis, C.

AU - Desai, S.

AU - Doel, P.

AU - Fausti Neto, A.

AU - Flaugher, B.

AU - Fosalba, P.

AU - Frieman, J.

AU - García-Bellido, J.

AU - Gerdes, D. W.

AU - Gruendl, R. A.

AU - Gschwend, J.

AU - Gutierrez, G.

AU - Honscheid, K.

AU - James, D. J.

AU - Jarvis, M.

AU - Jeltema, T.

AU - Kirk, D.

AU - Kuehn, K.

AU - Kuhlmann, S.

AU - Li, T. S.

AU - Lima, M.

AU - Maia, M. A.G.

AU - March, M.

AU - Suchyta, E.

PY - 2018/4/21

Y1 - 2018/4/21

N2 - We use a suite of simulated images based on Year 1 of the Dark Energy Survey to explore the impact of galaxy neighbours on shape measurement and shear cosmology. The HOOPOE image simulations include realistic blending, galaxy positions, and spatial variations in depth and point spread function properties. Using the IM3SHAPE maximum-likelihood shape measurement code, we identify four mechanisms by which neighbours can have a non-negligible influence on shear estimation. These effects, if ignored, would contribute a net multiplicative bias of m ~ 0.03-0.09 in the Year One of the Dark Energy Survey (DES Y1) IM3SHAPE catalogue, though the precise impact will be dependent on both the measurement code and the selection cuts applied. This can be reduced to percentage level or less by removing objects with close neighbours, at a cost to the effective number density of galaxies neff of 30 per cent. We use the cosmological inference pipeline of DES Y1 to explore the cosmological implications of neighbour bias and show that omitting blending from the calibration simulation for DES Y1 would bias the inferred clustering amplitude S8 ≡ σ8(Ωm/0.3)0.5 by 2σ towards low values. Finally, we use the HOOPOE simulations to test the effect of neighbour-induced spatial correlations in the multiplicative bias.We find the impact on the recovered S8 of ignoring such correlations to be subdominant to statistical error at the current level of precision.

AB - We use a suite of simulated images based on Year 1 of the Dark Energy Survey to explore the impact of galaxy neighbours on shape measurement and shear cosmology. The HOOPOE image simulations include realistic blending, galaxy positions, and spatial variations in depth and point spread function properties. Using the IM3SHAPE maximum-likelihood shape measurement code, we identify four mechanisms by which neighbours can have a non-negligible influence on shear estimation. These effects, if ignored, would contribute a net multiplicative bias of m ~ 0.03-0.09 in the Year One of the Dark Energy Survey (DES Y1) IM3SHAPE catalogue, though the precise impact will be dependent on both the measurement code and the selection cuts applied. This can be reduced to percentage level or less by removing objects with close neighbours, at a cost to the effective number density of galaxies neff of 30 per cent. We use the cosmological inference pipeline of DES Y1 to explore the cosmological implications of neighbour bias and show that omitting blending from the calibration simulation for DES Y1 would bias the inferred clustering amplitude S8 ≡ σ8(Ωm/0.3)0.5 by 2σ towards low values. Finally, we use the HOOPOE simulations to test the effect of neighbour-induced spatial correlations in the multiplicative bias.We find the impact on the recovered S8 of ignoring such correlations to be subdominant to statistical error at the current level of precision.

KW - Cosmological parameters

KW - Cosmology: observations

KW - Galaxies: statistics

KW - Gravitational lensing: weak

UR - http://www.scopus.com/inward/record.url?scp=85042531763&partnerID=8YFLogxK

U2 - 10.1093/mnras/stx3282

DO - 10.1093/mnras/stx3282

M3 - Article

AN - SCOPUS:85042531763

SN - 0035-8711

VL - 475

SP - 4524

EP - 4543

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

IS - 4

ER -

Dark Energy Survey Year 1 results: The impact of galaxy neighbours on weak lensing cosmology with IM3SHAPE

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