Validity of the Born approximation for beyond Gaussian weak lensing observables

Journal Article · Tue Jun 06 00:00:00 EDT 2017 · Physical Review. D.

DOI:https://doi.org/10.1103/PhysRevD.95.123503· OSTI ID:1362165

Petri, Andrea ^[1]; Haiman, Zoltan ^[2]; May, Morgan ^[1]

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1. Columbia Univ., New York, NY (United States). Dept. of Physics; Brookhaven National Lab. (BNL), Upton, NY (United States). Dept. of Physics
2. Columbia Univ., New York, NY (United States). Dept. of Astronomy; New York Univ. (NYU), NY (United States). Dept. of Physics

Accurate forward modeling of weak lensing (WL) observables from cosmological parameters is necessary for upcoming galaxy surveys. Because WL probes structures in the nonlinear regime, analytical forward modeling is very challenging, if not impossible. Numerical simulations of WL features rely on ray tracing through the outputs of N-body simulations, which requires knowledge of the gravitational potential and accurate solvers for light ray trajectories. A less accurate procedure, based on the Born approximation, only requires knowledge of the density field, and can be implemented more efficiently and at a lower computational cost. In this work, we use simulations to show that deviations of the Born-approximated convergence power spectrum, skewness and kurtosis from their fully ray-traced counterparts are consistent with the smallest nontrivial O(Φ³) post-Born corrections (so-called geodesic and lens-lens terms). Our results imply a cancellation among the larger O(Φ⁴) (and higher order) terms, consistent with previous analytic work. We also find that cosmological parameter bias induced by the Born-approximated power spectrum is negligible even for a LSST-like survey, once galaxy shape noise is considered. When considering higher order statistics such as the κ skewness and kurtosis, however, we find significant bias of up to 2.5σ. Using the LensTools software suite, we show that the Born approximation saves a factor of 4 in computing time with respect to the full ray tracing in reconstructing the convergence.

• Research Organization: Brookhaven National Laboratory (BNL), Upton, NY (United States)
• Sponsoring Organization: USDOE Office of Science (SC), High Energy Physics (HEP); National Science Foundation (NSF)
• Grant/Contract Number: SC0012704; ACI-1053575; AST-1210877
• OSTI ID: 1362165
• Alternate ID(s): OSTI ID: 1361575
• Report Number(s): BNL-113928-2017-JA; PRVDAQ
• Journal Information: Physical Review. D., Vol. 95, Issue 12; ISSN 2470-0010
• Publisher: American Physical Society (APS)
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
Weak gravitational lensing
Simulations
Methods numerical
analytical
statistical