Issue |
A&A
Volume 662, June 2022
|
|
---|---|---|
Article Number | A114 | |
Number of page(s) | 12 | |
Section | Numerical methods and codes | |
DOI | https://doi.org/10.1051/0004-6361/202142661 | |
Published online | 28 June 2022 |
Magrathea-Pathfinder: a 3D adaptive-mesh code for geodesic ray tracing in N-body simulations
1
Aix Marseille Univ, CNRS, CNES, LAM,
Marseille,
France
e-mail: breton@ice.csic.es
2
Institute of Space Sciences (ICE, CSIC), Campus UAB,
Carrer de Can Magrans, s/n,
08193
Barcelona,
Spain
3
Institut d'Estudis Espacials de Catalunya (IEEC),
Carrer Gran Capita 2-4,
08193
Barcelona,
Spain
4
National Center for Supercomputing Applications (NCSA), University of Illinois at Urbana-Champaign,
Urbana,
IL,
USA
e-mail: vince.rev@gmail.com
5
Laboratoire Univers et Théories, Observatoire de Paris, Université PSL, Université de Paris, CNRS,
92190
Meudon,
France
Received:
14
November
2021
Accepted:
4
March
2022
We introduce MAGRATHEA-PATHFINDER, a relativistic ray-tracing framework that can reconstruct the past light cone of observers in cosmological simulations. The code directly computes the 3D trajectory of light rays through the null geodesic equations, with the weak-field limit as its only approximation. This approach offers high levels of versatility while removing the need for many of the standard ray-tracing approximations such as plane-parallel, Born, or multiple-lens. Moreover, the use of adaptive integration steps and interpolation strategies based on adaptive-mesh refinement grids allows MAGRATHEA-PATHFINDER to accurately account for the nonlinear regime of structure formation and fully take advantage of the small-scale gravitational clustering. To handle very large N-body simulations, the framework has been designed as a high-performance computing post-processing tool relying on a hybrid paralleliza-tion that combines MPI tasks with C++11 std::threads. In this paper, we describe how realistic cosmological observables can be computed from numerical simulation using ray-tracing techniques. We discuss in particular the production of simulated catalogues and sky maps that account for all the observational effects considering first-order metric perturbations (such as peculiar velocities, gravitational potential, integrated Sachs-Wolfe, time-delay, and gravitational lensing). We perform convergence tests of our gravitational lensing algorithms and conduct performance benchmarks of the null geodesic integration procedures. MAGRATHEA-PATHFINDER introduces sophisticated ray-tracing tools to make the link between the space of N-body simulations and light-cone observables. This should provide new ways of exploring existing cosmological probes and building new ones beyond standard assumptions in order to prepare for the next generation of large-scale structure surveys.
Key words: large-scale structure of Universe / methods: numerical / gravitation / gravitational lensing: weak
© M.-A. Breton and V. Reverdy 2022
Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
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