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

DES Collaboration

Research output: Contribution to journalArticle

16 Citations (Scopus)

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 ≡ σ8m/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 languageEnglish (US)
Pages (from-to)4524-4543
Number of pages20
JournalMonthly Notices of the Royal Astronomical Society
Volume475
Issue number4
DOIs
StatePublished - Apr 21 2018
Externally publishedYes

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cosmology
dark energy
galaxies
simulation
energy
shear
spatial variation
point spread functions
inference
calibration
catalogs
costs
cost
code
effect

Keywords

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

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

Cite this

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

In: Monthly Notices of the Royal Astronomical Society, Vol. 475, No. 4, 21.04.2018, p. 4524-4543.

Research output: Contribution to journalArticle

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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(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.",
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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 Marshall, {J. L.}",
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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 - Marshall, J. L.

PY - 2018/4/21

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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

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DO - 10.1093/mnras/stx3282

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