Non-linear CMB lensing with neutrinos and baryons: FLAMINGO simulations vs. fast approximations

Amol Upadhye; Juliana Kwan; Ian G. McCarthy; Jaime Salcido; John C. Helly; Roi Kugel; Matthieu Schaller; Joop Schaye; Joey Braspenning; Willem Elbers; Carlos S. Frenk; Marcel P. van Daalen; Bert Vandenbroucke; Jeger C. Broxterman

arXiv · 2308.09755

Non-linear CMB lensing with neutrinos and baryons: FLAMINGO simulations vs. fast approximations

Amol Upadhye·Juliana Kwan·Ian G. McCarthy·Jaime Salcido·John C. Helly·Roi Kugel·Matthieu Schaller·Joop Schaye·Joey Braspenning·Willem Elbers·Carlos S. Frenk·Marcel P. van Daalen·Bert Vandenbroucke·Jeger C. Broxterman

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Abstract

Weak lensing of the cosmic microwave background is rapidly emerging as a powerful probe of neutrinos, dark energy, and new physics. We present a fast computation of the non-linear CMB lensing power spectrum which combines non-linear perturbation theory at early times with power spectrum emulation using cosmological simulations at late times. Comparing our calculation with lightcones from the FLAMINGO 5.6 Gpc cube dark-matter-only simulation, we confirm its accuracy to 1% (2%) up to multipoles L = 3000 (L = 5000) for a nuLambdaCDM cosmology consistent with current data. Clustering suppression due to small-scale baryonic phenomena such as feedback from active galactic nuclei can reduce the lensing power by of order 10%. To our perturbation theory and emulator-based calculation we add SP(k), a new fitting function for this suppression, and confirm its accuracy compared to the FLAMINGO hydrodynamic simulations to 4% at L = 5000, with similar accuracy for massive neutrino models. We further demonstrate that scale-dependent suppression due to neutrinos and baryons approximately factorize, implying that a careful treatment of baryonic feedback can limit biasing neutrino mass constraints.

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Amol Upadhye, Juliana Kwan, Ian G. McCarthy, Jaime Salcido, John C. Helly, Roi Kugel, Matthieu Schaller, Joop Schaye, Joey Braspenning, Willem Elbers, Carlos S. Frenk, Marcel P. van Daalen, Bert Vandenbroucke, Jeger C. Broxterman. 2023-08-18. Non-linear CMB lensing with neutrinos and baryons: FLAMINGO simulations vs. fast approximations. https://arxiv.org/abs/2308.09755

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