Monte Carlo control loops for cosmic shear cosmology with DES Year 1 data
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Weak lensing by large-scale structure is a powerful probe of cosmology and of the dark universe. This cosmic shear technique relies on the accurate measurement of the shapes and redshifts of background galaxies and requires precise control of systematic errors. Monte Carlo control loops (MCCL) is a forward modeling method designed to tackle this problem. It relies on the ultra fast image generator (UFig) to produce simulated images tuned to match the target data statistically, followed by calibrations and tolerance loops. Here, we present the first end-to-end application of this method, on the Dark Energy Survey (DES) Year 1 wide field imaging data. We simultaneously measure the shear power spectrum $$C_ℓ$$ and the redshift distribution $n(z)$ of the background galaxy sample. The method includes maps of the systematic sources, point spread function (PSF), an approximate Bayesian computation (ABC) inference of the simulation model parameters, a shear calibration scheme, and a fast method to estimate the covariance matrix. We find a close statistical agreement between the simulations and the DES Y1 data using an array of diagnostics. In a nontomographic setting, we derive a set of $$C_ℓ$$ and $n(z)$ curves that encode the cosmic shear measurement, as well as the systematic uncertainty. Following a blinding scheme, we measure the combination of $$Ω_m$$, $$σ_8$$, and intrinsic alignment amplitude $$A_{IA}$$, defined as $$S_8D_{IA}=σ_8(Ω_m/0.3)^{0.5}D_{IA}$$, where $$D_{IA}=1-0.11(A_{IA}-1)$$. We find $$S_8D_{IA}=0.8954_{-0.039}^{+0.054}$$, where systematics are at the level of roughly 60% of the statistical errors. We discuss these results in the context of earlier cosmic shear analyses of the DES Y1 data. Our findings indicate that this method and its fast runtime offer good prospects for cosmic shear measurements with future wide-field surveys.
- Research Organization:
- SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States); Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), High Energy Physics (HEP); Swiss National Science Foundation (SNSF), National Science Foundation (NSF); Ministry of Science and Education of Spain; Science and Technology Facilities Council (STFC) (United Kingdom); European Union (EU)
- Contributing Organization:
- The DES Collaboration; DES Collaboration
- Grant/Contract Number:
- AC02-76SF00515; 200021_169130; AST-1138766; AST-1536171; 465376/2014-2; AYA2015-71825; ESP2015-66861; FPA2015-68048; SEV-2016-0588; SEV-2016-0597; MDM-2015-0509; FP7/2007-2013; 240672; 291329; 306478; AC02-07CH11359; AC05-00OR22725
- OSTI ID:
- 1633431
- Alternate ID(s):
- OSTI ID: 1661217
- Journal Information:
- Physical Review. D., Vol. 101, Issue 8; ISSN 2470-0010
- Publisher:
- American Physical Society (APS)Copyright Statement
- Country of Publication:
- United States
- Language:
- English
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