Paper

Euclid preparation. LIII. LensMC, weak lensing cosmic shear measurement with forward modelling and Markov Chain Monte Carlo sampling

S Di Domizio, Auricchio, N, Cabanac, R, Cañas-Herrera, G, Andreon, S, Rossetti, E, Metcalf, R B, Morin, B, Finelli, F, Potter, D, Keihänen, E, García-Bellido, J, Troja, A, C J A P Martins, Reimberg, P, Aghanim, N, Bruton, S, Castro, T, Degaudenzi, H, Viel, M, Steinwagner, J, Maggio, G, Holliman, M S, Zoubian, J, Tewes, M, Welikala, N, Conversi, L, Jahnke, K, Dupac, X, Saglia, R, Schneider, P, Cimatti, A, Kurki-Suonio, H, Conselice, C J, Desprez, G, Zucca, E, Hildebrandt, H, Cropper, M, Hall, A, Schneider, A, Capobianco, V, Macias-Perez, J, Allevato, V, Burigana, C, Moresco, M, Lindholm, V, Gozaliasl, G, Tutusaus, I, Haugan, S V H, Peel, A, Neissner, C, Vergani, D, Merlin, E, Coupon, J, Pozzetti, L, Wang, Y, Amara, A, Sartoris, B, Ferrero, I, Cardone, V F, Rebolo, R, Tavagnacco, D, Marulli, F, Castignani, G, Munari, E, Simon, P, Franceschi, E, Giacomini, F, Seidel, G, Torradeflot, F, Fosalba, P, Bolzonella, M, Bozzo, E, S -M Niemi, Tereno, I, Gillis, B, Karagiannis, D, Popa, V, Borgani, S, Bonino, D, Schrabback, T, A Jimenez Muñoz, Kitching, T, Kubik, B, Stadel, J, Sakr, Z, Roncarelli, M, Baccigalupi, C, Maino, D, Pöntinen, M, Branchini, E, Holmes, W, Monaco, P, Bresci

2024

Overview

LensMC is a weak lensing shear measurement method developed for Euclid and Stage-IV surveys. It is based on forward modelling in order to deal with convolution by a point spread function (PSF) with comparable size to many galaxies; sampling the posterior distribution of galaxy parameters via Markov Chain Monte Carlo; and marginalisation over nuisance parameters for each of the 1.5 billion galaxies observed by Euclid. We quantified the scientific performance through high-fidelity images based on the Euclid Flagship simulations and emulation of the Euclid VIS images; realistic clustering with a mean surface number density of 250 arcmin\\(^{-2}\\) (\\(I_{\\rm E}<29.5\\)) for galaxies, and 6 arcmin\\(^{-2}\\) (\\(I_{\\rm E}<26\\)) for stars; and a diffraction-limited chromatic PSF with a full width at half maximum of \\(0.^{\\!\\prime\\prime}2\\) and spatial variation across the field of view. LensMC measured objects with a density of 90 arcmin\\(^{-2}\\) (\\(I_{\\rm E}<26.5\\)) in 4500 deg\\(^2\\). The total shear bias was broken down into measurement (our main focus here) and selection effects (which will be addressed elsewhere). We found measurement multiplicative and additive biases of \\(m_1=(-3.6\\pm0.2)\\times10^{-3}\\), \\(m_2=(-4.3\\pm0.2)\\times10^{-3}\\), \\(c_1=(-1.78\\pm0.03)\\times10^{-4}\\), \\(c_2=(0.09\\pm0.03)\\times10^{-4}\\); a large detection bias with a multiplicative component of \\(1.2\\times10^{-2}\\) and an additive component of \\(-3\\times10^{-4}\\); and a measurement PSF leakage of \\(\\alpha_1=(-9\\pm3)\\times10^{-4}\\) and \\(\\alpha_2=(2\\pm3)\\times10^{-4}\\). When model bias is suppressed, the obtained measurement biases are close to Euclid requirement and largely dominated by undetected faint galaxies (\\(-5\\times10^{-3}\\)). Although significant, model bias will be straightforward to calibrate given the weak sensitivity. LensMC is publicly available at https://gitlab.com/gcongedo/LensMC

• Publisher: Cornell University Library, arXiv.org
• Subject: Bias / Clustering / Density / Galaxy distribution / Markov analysis / Markov chains / Mathematical models / Measurement methods / Modelling / Parameters / Point spread functions / Sampling / Shear