The impact of baryons on weak lensing statistics as a function of halo mass and radius

Abstract

Upcoming weak lensing (WL) surveys such as those by {\it Euclid}, LSST, and {\it Roman} require percent-level control over systematic effects. A common approach to mitigating baryonic effects uses semi-analytic baryon correction models (BCMs) that modify halo profiles in dark matter-only (DMO) simulations, calibrated to statistics from hydrodynamic simulations. We investigate the limits of this approach by progressively replacing larger regions around halos of decreasing mass in DMO simulations with their hydrodynamical counterparts. We compare multiple statistics -- the matter ($P(k)$) and weak-lensing ($C_{\ell }$) power spectra, peak counts, minima, one-point PDFs, and Minkowski functionals -- from "Replace" fields against hydrodynamical and DMO simulations. We find that replacing all halos with $M\ge 10^{12}{h}^{-1}{\mathrm{M}}_{\odot }$ out to $r\le 5R_{200}$ recovers $\sim 90\%$ of the baryonic suppression in $P(k)$ and $C_{\ell }$ with the remaining $\sim 10\%$ originating from lower-mass halos or material farther outside of DM halos. Each statistic has distinct sensitivities to baryons: $P(k)$ and $C_{\ell }$ are sensitive to a broad range of masses and radii, whereas WL peaks are primarily affected by the cores of massive halos. We show that BCMs applied to massive halos and calibrated to match hydrodynamical $P(k)$ make two cancelling "mistakes": they underpredict core masses and compensate by overpredicting baryonic impacts at larger radii, thereby explaining previously reported failures of peak statistics in these models. We provide a framework for diagnosing critical mass/radius regions in baryonic modeling for a range of statistics for next-generation BCMs.

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