RAY-RAMSES: a code for ray tracing on the fly in N-body simulations

Abstract

We present a ray tracing code to compute integrated cosmological observables on the fly in AMR N-body simulations. Unlike conventional ray tracing techniques, our code takes full advantage of the time and spatial resolution attained by the N-body simulation by computing the integrals along the line of sight on a cell-by-cell basis through the AMR simulation grid. Moroever, since it runs on the fly in the N-body run, our code can produce maps of the desired observables without storing large (or any) amounts of data for post-processing. We implemented our routines in the RAMSES N-body code and tested the implementation using an example of weak lensing simulation. We analyse basic statistics of lensing convergence maps and find good agreement with semi-analytical methods. The ray tracing methodology presented here can be used in several cosmological analysis such as Sunyaev-Zel'dovich and integrated Sachs-Wolfe effect studies as well as modified gravity. Our code can also be used in cross-checks of the more conventional methods, which can be important in tests of theory systematics in preparation for upcoming large scale structure surveys.

28 pages, 13 figures. v2 published in JCAP

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Cited by in corpus (19)

• Weak lensing for precision cosmology
• Weak Lensing Light-Cones in Modified Gravity simulations with and without Massive Neutrinos
• On the validity of the Born approximation for beyond-Gaussian weak lensing observables
• Modelling Void Abundance in Modified Gravity
• Imprints of relativistic effects on the asymmetry of the halo cross-correlation function: from linear to non-linear scales
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• On the dissection of degenerate cosmologies with machine learning
• Weak lensing by voids in weak lensing maps
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• Cosmological test of gravity using weak lensing voids
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• Isolating non-linearities of light propagation in inhomogeneous cosmologies
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• A Hamiltonian, post-Born, three-dimensional, on-the-fly ray tracing algorithm for gravitational lensing