UCL Discovery Stage
UCL home » Library Services » Electronic resources » UCL Discovery Stage

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

Samuroff, S; Bridle, SL; Zuntz, J; Troxel, MA; Gruen, D; Rollins, RP; Bernstein, GM; ... Tucker, DL; + view all (2018) Dark Energy Survey Year 1 results: The impact of galaxy neighbours on weak lensing cosmology with IM3SHAPE. Monthly Notices of the Royal Astronomical Society , 475 (4) pp. 4524-4543. 10.1093/mnras/stx3282. Green open access

[thumbnail of Abdalla_stx3282.pdf]
Preview
Text
Abdalla_stx3282.pdf - Published Version

Download (4MB) | Preview

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 S 8 ≡ σ 8 (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 S 8 of ignoring such correlations to be subdominant to statistical error at the current level of precision.

Type: Article
Title: Dark Energy Survey Year 1 results: The impact of galaxy neighbours on weak lensing cosmology with IM3SHAPE
Open access status: An open access version is available from UCL Discovery
DOI: 10.1093/mnras/stx3282
Publisher version: https://academic.oup.com/mnras/article/475/4/4524/...
Language: English
Additional information: © 2017 The Author(s) Published by Oxford University Press on behalf of the Royal Astronomical Society.
Keywords: Gravitational lensing: weak, galaxies: statistics, cosmological parameters, cosmology: observations
UCL classification: UCL
UCL > Provost and Vice Provost Offices > UCL BEAMS
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences
UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Physics and Astronomy
URI: https://discovery-pp.ucl.ac.uk/id/eprint/1571420
Downloads since deposit
714Downloads
Download activity - last month
Download activity - last 12 months
Downloads by country - last 12 months

Archive Staff Only

View Item View Item