# Weak Lensing Minima and Peaks: Cosmological Constraints and the Impact of Baryons

Coulton, WR, Liu, J, McCarthy, IG and Osato, K (2020) Weak Lensing Minima and Peaks: Cosmological Constraints and the Impact of Baryons. Monthly Notices of the Royal Astronomical Society, 495 (3). pp. 2531-2542. ISSN 0035-8711

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We present a novel statistic to extract cosmological information in weak lensing data: the lensing minima. We also investigate the effect of baryons on the cosmological constraints from peak and minimum counts. Using the \texttt{MassiveNuS} simulations, we find that lensing minima are sensitive to non-Gaussian cosmological information and are complementary to the lensing power spectrum and peak counts. For an LSST-like survey, we obtain $95\%$ credible intervals from a combination of lensing minima and peaks that are significantly stronger than from the power spectrum alone, by $44\%$, $11\%$, and $63\%$ for the neutrino mass sum $\sum m_\nu$, matter density $\Omega_m$, and amplitude of fluctuation $A_s$, respectively. We explore the effect of baryonic processes on lensing minima and peaks using the hydrodynamical simulations \texttt{BAHAMAS} and \texttt{Osato15}. We find that ignoring baryonic effects would lead to strong ($\approx 4 \sigma$) biases in inferences from peak counts, but negligible ($\approx 0.5 \sigma$) for minimum counts, suggesting lensing minima are a potentially more robust tool against baryonic effects. Finally, we demonstrate that the biases can in principle be mitigated without significantly degrading cosmological constraints when we model and marginalize the baryonic effects.