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

Abstract

In this work, 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 percent. 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. Lastly, we use the hoopoe simulations to test the effect of neighbour-inducedmore » 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.« less

Authors:
 [1]
  1. Univ. of Manchester (United Kingdom). et al.
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL), Upton, NY (United States); SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Fermi National Accelerator Laboratory (FNAL), Batavia, IL (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org.:
USDOE Office of Science (SC), High Energy Physics (HEP); USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR)
Contributing Org.:
DES Collaboration
OSTI Identifier:
1376073
Alternate Identifier(s):
OSTI ID: 1392237; OSTI ID: 1426560
Report Number(s):
FERMILAB-PUB-17-291-E; arXiv:1708.01534; BNL-114252-2017-JA
Journal ID: ISSN 0035-8711; 1614457
Grant/Contract Number:  
AC02-07CH11359; SC0012704; AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Monthly Notices of the Royal Astronomical Society
Additional Journal Information:
Journal Volume: 475; Journal Issue: 4; Journal ID: ISSN 0035-8711
Publisher:
Royal Astronomical Society
Country of Publication:
United States
Language:
English
Subject:
79 ASTRONOMY AND ASTROPHYSICS; gravitational lensing: weak; galaxies: statistics; cosmological parameters; cosmology: observations

Citation Formats

Samuroff, S. Dark Energy Survey Year 1 results: the impact of galaxy neighbours on weak lensing cosmology with IM3SHAPE. United States: N. p., 2017. Web. doi:10.1093/mnras/stx3282.
Samuroff, S. Dark Energy Survey Year 1 results: the impact of galaxy neighbours on weak lensing cosmology with IM3SHAPE. United States. https://doi.org/10.1093/mnras/stx3282
Samuroff, S. 2017. "Dark Energy Survey Year 1 results: the impact of galaxy neighbours on weak lensing cosmology with IM3SHAPE". United States. https://doi.org/10.1093/mnras/stx3282. https://www.osti.gov/servlets/purl/1376073.
@article{osti_1376073,
title = {Dark Energy Survey Year 1 results: the impact of galaxy neighbours on weak lensing cosmology with IM3SHAPE},
author = {Samuroff, S.},
abstractNote = {In this work, 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 percent. 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. Lastly, 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.},
doi = {10.1093/mnras/stx3282},
url = {https://www.osti.gov/biblio/1376073}, journal = {Monthly Notices of the Royal Astronomical Society},
issn = {0035-8711},
number = 4,
volume = 475,
place = {United States},
year = {Tue Dec 26 00:00:00 EST 2017},
month = {Tue Dec 26 00:00:00 EST 2017}
}

Journal Article:
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Cited by: 41 works
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Figures / Tables:

Figure-1 Figure-1: Postage stamp snapshots of the basic two-object toy model described in Section 3. The overlain ellipse shows the maximum likelihood fit to the image. The panels show three neighbour positions in the range θ = [0, π/2] rad. The best-fitting ellipticity and half-light radius are shown above each image.more » In all cases the input values are e = (0, 0), r = 0.5 arcsec.« less

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Works referencing / citing this record:

Cosmological simulations for combined-probe analyses: covariance and neighbour-exclusion bias
journal, August 2018


Euclid preparation : IV. Impact of undetected galaxies on weak-lensing shear measurements⋆
journal, July 2019


Cosmic shear: Inference from forward models
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Cosmological lensing ratios with DES Y1, SPT, and Planck
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Weak lensing shear calibration with simulations of the HSC survey
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Towards emulating cosmic shear data: revisiting the calibration of the shear measurements for the Kilo-Degree Survey
journal, April 2019


Dark Energy Survey Year 1 results: weak lensing shape catalogues
journal, August 2018


Cosmic Shear: Inference from Forward Models
text, January 2019


Image Simulations for Strong and Weak Gravitational Lensing
journal, March 2020