Abstract
ABSTRACT Measurements of large-scale structure are interpreted using theoretical predictions for the matter distribution, including potential impacts of baryonic physics. We constrain the feedback strength of baryons jointly with cosmology using weak lensing and galaxy clustering observables (3 × 2pt) of Dark Energy Survey (DES) Year 1 data in combination with external information from baryon acoustic oscillations (BAO) and Planck cosmic microwave background polarization. Our baryon modelling is informed by a set of hydrodynamical simulations that span a variety of baryon scenarios; we span this space via a Principal Component (PC) analysis of the summary statistics extracted from these simulations. We show that at the level of DES Y1 constraining power, one PC is sufficient to describe the variation of baryonic effects in the observables, and the first PC amplitude (Q1) generally reflects the strength of baryon feedback. With the upper limit of Q1 prior being bound by the Illustris feedback scenarios, we reach $\sim 20{{\ \rm per\ cent}}$ improvement in the constraint of $S_8=\sigma _8(\Omega _{\rm m}/0.3)^{0.5}=0.788^{+0.018}_{-0.021}$ compared to the original DES 3 × 2pt analysis. This gain is driven by the inclusion of small-scale cosmic shear information down to 2.5 arcmin, which was excluded in previous DES analyses that did not model baryonic physics. We obtain $S_8=0.781^{+0.014}_{-0.015}$ for the combined DES Y1+Planck EE+BAO analysis with a non-informative Q1 prior. In terms of the baryon constraints, we measure $Q_1=1.14^{+2.20}_{-2.80}$ for DES Y1 only and $Q_1=1.42^{+1.63}_{-1.48}$ for DESY1+Planck EE+BAO, allowing us to exclude one of the most extreme AGN feedback hydrodynamical scenario at more than 2σ.
Highlights
Understanding the composition and evolution of our Universe has been a central science endeavor in the astronomical community
One of the fundamental quantities for making theoretical predictions is the matter power spectrum Pδ (k, z), which quantifies the amount of matter clustering at the second-order level and its evolution as a function of time
In Huang et al (2019), we have validated and improved the performance of the principal component analyses (PCA) method using simulated analyses of cosmic shear mock data under an LSST-like survey configuration
Summary
Understanding the composition and evolution of our Universe has been a central science endeavor in the astronomical community. To quantify the nonlinear evolution of the density field at the required precision, significant computational resources have been devoted to building power spectrum emulators with N-body darkmatter-only (DMO) simulations (e.g., Heitmann et al 2010, 2014; DeRose et al 2019). Baryonic effects such as feedback and cooling mechanisms redistribute matter, causing uncertainties in Pδ (k, z) at the level of tens of per cent (e.g., van Daalen et al 2011; Chisari et al 2018; van Daalen et al 2020) for k 5 hMpc−1
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