Merlin: Fast and flexible 3x2pt cosmology with simulation-based inference

arXiv (Cornell University)

Abstract

We present Merlin, a simulation-based inference (SBI) pipeline to perform cosmological analyses of 3x2pt summary statistics: cosmic shear, galaxy clustering and the cross-correlation power spectra. Our approach combines Marginal Neural Ratio Estimation (MNRE) with 3x2pt angular power spectra predictions from the cloelib library, although the pipeline is readily extensible to other cosmology libraries. We demonstrate this pipeline on a realistic setting representative of a Stage-IV photometric survey, with a 50-dimensional parameter space describing cosmology and a wide range of systematic effects. We find posteriors that are in excellent agreement with the nested sampler Nautilus, while reducing the number of required CPU-hours by two orders of magnitude. Because the generation of training data and the training of inference networks are decoupled processes, a single simulation bank can be reused to perform inference under different analysis choices, further improving the simulator-efficiency. We illustrate this flexibility by applying scale cuts, varying the survey area, and removing cosmic shear from the data vector (2x2pt), all at zero extra model evaluations, whereas sampling-based methods need costly re-runs for each case. The Merlin code is publicly available on GitHub.

Authors 3

1. Alexandra Wernersson

   National Institute for Subatomic Physics · Halmstad University

   Affiliation as printed

   CAISR Health , Halmstad University , Halmstad 30118 , Sweden

   Nikhef , Science Park 105 , 1098 XG , Amsterdam , The Netherlands

2. Guillermo Franco-Abellán

   Consejo Superior de Investigaciones Científicas · Universitat de València · Instituto de Física Corpuscular

   Affiliation as printed

   IFIC , CSIC-Universitat de València , c/ Catedrático José Beltrán , 2 E-46980 Paterna , Spain

3. Guadalupe Cañas-Herrera Aachen Leiden Observatory

   Leiden University · Leiden Observatory

   Affiliation as printed

   Leiden Observatory , Leiden University , PO Box 9506 , Leiden 2300 RA , The Netherlands