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Euclid: The reduced shear approximation and magnification bias for Stage IV cosmic shear experiments

Deshpande, A. C. and Kitching, T. D. and Cardone, V. F. and Taylor, P. L. and Casas, S. and Camera, S. and Carbone, C. and Kilbinger, M. and Pettorino, V. and Sakr, Z. and Sapone, D. and Tutusaus, I. and Auricchio, N. and Bodendorf, C. and Bonino, D. and Brescia, M. and Capobianco, V. and Carretero, J. and Castellano, M. and Cavuoti, S. and Cledassou, R. and Congedo, G. and Conversi, L. and Corcione, L. and Cropper, M. and Dubath, F. and Dusini, S. and Fabbian, G. and Franceschi, E. and Fumana, M. and Garilli, B. and Grupp, F. and Hoekstra, H. and Hormuth, F. and Israel, H. and Jahnke, K. and Kermiche, S. and Kubik, B. and Kunz, M. and Lacasa, F. and Ligori, S. and Lilje, P. B. and Lloro, I. and Maiorano, E. and Marggraf, O. and Massey, R. and Mei, S. and Meneghetti, M. and Meylan, G. and Moscardini, L. and Padilla, C. and Paltani, S. and Pasian, F. and Pires, S. and Polenta, G. and Poncet, M. and Raison, F. and Rhodes, J. and Roncarelli, M. and Saglia, R. and Schneider, P. and Secroun, A. and Serrano, S. and Sirri, G. and Starck, J. L. and Sureau, F. and Taylor, A. N. and Tereno, I. and Toledo-Moreo, R. and Valenziano, L. and Wang, Y. and Zoubian, J. (2020) Euclid: The reduced shear approximation and magnification bias for Stage IV cosmic shear experiments. Astronomy and Astrophysics, 636 . Art. No. A95. ISSN 0004-6361. doi:10.1051/0004-6361/201937323.

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Context. Stage IV weak lensing experiments will offer more than an order of magnitude leap in precision. We must therefore ensure that our analyses remain accurate in this new era. Accordingly, previously ignored systematic effects must be addressed. Aims. In this work, we evaluate the impact of the reduced shear approximation and magnification bias on information obtained from the angular power spectrum. To first-order, the statistics of reduced shear, a combination of shear and convergence, are taken to be equal to those of shear. However, this approximation can induce a bias in the cosmological parameters that can no longer be neglected. A separate bias arises from the statistics of shear being altered by the preferential selection of galaxies and the dilution of their surface densities in high-magnification regions. Methods. The corrections for these systematic effects take similar forms, allowing them to be treated together. We calculated the impact of neglecting these effects on the cosmological parameters that would be determined from Euclid, using cosmic shear tomography. To do so, we employed the Fisher matrix formalism, and included the impact of the super-sample covariance. We also demonstrate how the reduced shear correction can be calculated using a lognormal field forward modelling approach. Results. These effects cause significant biases in Ω_m, σ₈, n_s, Ω_(DE), w₀, and w_a of −0.53σ, 0.43σ, −0.34σ, 1.36σ, −0.68σ, and 1.21σ, respectively. We then show that these lensing biases interact with another systematic effect: the intrinsic alignment of galaxies. Accordingly, we have developed the formalism for an intrinsic alignment-enhanced lensing bias correction. Applying this to Euclid, we find that the additional terms introduced by this correction are sub-dominant.

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Deshpande, A. C.0000-0003-3721-4232
Alternate Title:Euclid: On the reduced shear approximation and magnification bias for Stage IV cosmic shear experiments
Additional Information:© 2020 ESO. Article published by EDP Sciences. Received 16 December 2019; Accepted 4 March 2020; Published online 27 April 2020. This paper is published on behalf of the Euclid Consortium. We thank the anonymous referee for their constructive comments, and Paniez Paykari for her programming expertise. ACD and TDK are supported by the Royal Society. PLT acknowledges support for this work from a NASA Postdoctoral Program Fellowship and the UK Science and Technologies Facilities Council. Part of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. The Euclid Consortium acknowledges the European Space Agency and the support of a number of agencies and institutes that have supported the development of Euclid, in particular the Academy of Finland, the Agenzia Spaziale Italiana, the Belgian Science Policy, the Canadian Euclid Consortium, the Centre National d’Etudes Spatiales, the Deutsches Zentrum für Luft- und Raumfahrt, the Danish Space Research Institute, the Fundação para a Ciência e a Tecnologia, the Ministerio de Economia y Competitividad, the National Aeronautics and Space Administration, the Netherlandse Onderzoekschool Voor Astronomie, the Norwegian Space Agency, the Romanian Space Agency, the State Secretariat for Education, Research and Innovation (SERI) at the Swiss Space Office (SSO), and the United Kingdom Space Agency. A detailed complete list is available on the Euclid web site (
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
NASA Postdoctoral ProgramUNSPECIFIED
Science and Technologies Facilities Council (STFC)UNSPECIFIED
European Space Agency (ESA)UNSPECIFIED
Academy of FinlandUNSPECIFIED
Agenzia Spaziale ItalianaUNSPECIFIED
Belgian Federal Science Policy Office (BELSPO)UNSPECIFIED
Canadian Euclid ConsortiumUNSPECIFIED
Centre National de la Recherche Scientifique (CNRS)UNSPECIFIED
Deutsches Zentrum für Luft- und Raumfahrt (DLR)UNSPECIFIED
Danish Space Research InstituteUNSPECIFIED
Fundação para a Ciência e a Tecnologia (FCT)UNSPECIFIED
Ministerio de Economia y ComNetherlanpetitividad (MINECO)UNSPECIFIED
Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO)UNSPECIFIED
Norwegian Space AgencyUNSPECIFIED
Romanian Space AgencyUNSPECIFIED
State Secretariat for Education, Research and Innovation (SERI)UNSPECIFIED
Swiss Space Office (SSO)UNSPECIFIED
United Kingdom Space Agency (UKSA)UNSPECIFIED
Subject Keywords:gravitational lensing: weak – cosmology: observations – methods: analytical
Record Number:CaltechAUTHORS:20200427-101700675
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Official Citation:Euclid: The reduced shear approximation and magnification bias for Stage IV cosmic shear experiments. A. C. Deshpande, T. D. Kitching, V. F. Cardone, P. L. Taylor, S. Casas, S. Camera, C. Carbone, M. Kilbinger, V. Pettorino, Z. Sakr, D. Sapone, I. Tutusaus, N. Auricchio, C. Bodendorf, D. Bonino, M. Brescia, V. Capobianco, J. Carretero, M. Castellano, S. Cavuoti, R. Cledassou, G. Congedo, L. Conversi, L. Corcione, M. Cropper, F. Dubath, S. Dusini, G. Fabbian, E. Franceschi, M. Fumana, B. Garilli, F. Grupp, H. Hoekstra, F. Hormuth, H. Israel, K. Jahnke, S. Kermiche, B. Kubik, M. Kunz, F. Lacasa, S. Ligori, P. B. Lilje, I. Lloro, E. Maiorano, O. Marggraf, R. Massey, S. Mei, M. Meneghetti, G. Meylan, L. Moscardini, C. Padilla, S. Paltani, F. Pasian, S. Pires, G. Polenta, M. Poncet, F. Raison, J. Rhodes, M. Roncarelli, R. Saglia, P. Schneider, A. Secroun, S. Serrano, G. Sirri, J. L. Starck, F. Sureau, A. N. Taylor, I. Tereno, R. Toledo-Moreo, L. Valenziano, Y. Wang and J. Zoubian. A&A, 636 (2020) A95; DOI:
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:102798
Deposited By: Tony Diaz
Deposited On:27 Apr 2020 17:56
Last Modified:16 Nov 2021 18:15

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