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

• Published in: Monthly notices of the Royal Astronomical Society Vol. 529; no. 2; pp. 1862 - 1876
• Main Authors: Upadhye, Amol, Kwan, Juliana, McCarthy, Ian G, Salcido, Jaime, Helly, John C, Kugel, Roi, Schaller, Matthieu, Schaye, Joop, Braspenning, Joey, Elbers, Willem, Frenk, Carlos S, van Daalen, Marcel P, Vandenbroucke, Bert, Broxterman, Jeger C
• Format: Journal Article
• Language: English
• Published: 06.03.2024
• ISSN: 0035-8711; 1365-2966
• DOI: 10.1093/mnras/stae663

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 that combines non-linear perturbation theory at early times with power spectrum emulation using cosmological simulations at late times. Comparing our calculation with light-cones from the FLAMINGO 5.6 Gpc cube dark-matter-only simulation, we confirm its accuracy to $1{{\ \rm per\ cent}}$ ($2{{\ \rm per\ cent}}$) up to multipoles L = 3000 (L = 5000) for a νΛCDM 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 $\sim 10{{\ \rm per\ cent}}$. 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 $4{{\ \rm per\ cent}}$ 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.