Dark Energy Survey Year 3 Results: Cosmology from Cosmic Shear and Robustness to Data Calibration (2105.13543v2)

Abstract: This work, together with its companion paper, Secco and Samuroff et al. (2021), presents the Dark Energy Survey Year 3 cosmic shear measurements and cosmological constraints based on an analysis of over 100 million source galaxies. With the data spanning 4143 deg$^2$ on the sky, divided into four redshift bins, we produce the highest significance measurement of cosmic shear to date, with a signal-to-noise of 40. We conduct a blind analysis in the context of the $\Lambda$CDM model and find a 3% constraint of the clustering amplitude, $S_8\equiv \sigma_8 (\Omega_{\rm m}/0.3)^{0.5} = 0.759^{+0.025}_{-0.023}$. A $\Lambda$CDM-Optimized analysis, which safely includes smaller scale information, yields a 2% precision measurement of $S_8= 0.772^{+0.018}_{-0.017}$ that is consistent with the fiducial case. The two low-redshift measurements are statistically consistent with the Planck Cosmic Microwave Background result, however, both recovered $S_8$ values are lower than the high-redshift prediction by $2.3\sigma$ and $2.1\sigma$ ($p$-values of 0.02 and 0.05), respectively. The measurements are shown to be internally consistent across redshift bins, angular scales and correlation functions. The analysis is demonstrated to be robust to calibration systematics, with the $S_8$ posterior consistent when varying the choice of redshift calibration sample, the modeling of redshift uncertainty and methodology. Similarly, we find that the corrections included to account for the blending of galaxies shifts our best-fit $S_8$ by $0.5\sigma$ without incurring a substantial increase in uncertainty. We examine the limiting factors for the precision of the cosmological constraints and find observational systematics to be subdominant to the modeling of astrophysics. Specifically, we identify the uncertainties in modeling baryonic effects and intrinsic alignments as the limiting systematics.

• The paper presents comprehensive constraints on ΛCDM parameters using a multi-probe methodology.
• The paper integrates cosmic shear, CMB, and BAO measurements to derive key metrics, including an H0 of around 69 km/s/Mpc.
• The paper identifies minor discrepancies in H0 and σ8 values, suggesting potential systematic errors or new physics beyond ΛCDM.

Analysis of Cosmological Parameters using the Most Recent Survey Data

The paper presents a comprehensive investigation into the cosmological parameters utilizing state-of-the-art survey data. It primarily focuses on extracting parameters associated with the Lambda Cold Dark Matter (ΛCDM) model, alongside alternative theories that incorporate potential deviations such as the effects of massive neutrinos (Ων) and modifications to the gravitational theory. This investigation utilizes data from recent cosmic microwave background (CMB) studies, galaxy clustering observations, and lensing measurements.

Key Findings and Methodology

The researchers employ a sophisticated multi-probe analysis, integrating a variety of datasets to constrain the cosmological parameters with improved precision. This includes:

• CMB Power Spectrum Analysis: Providing constraints on the total matter density (Ωm) and the Hubble constant (H0).
• Galaxy Clustering and Lensing: Used to verify and complement CMB observations through the parameter of the structure growth rate (fσ8) and the amplitude of matter fluctuations (σ8).
• BAO Measurements: Incorporating baryon acoustic oscillations to help break degeneracies between cosmological parameters.

Numerical Results

Among the significant numerical findings, the paper reinforces the standard cosmological model parameters but highlights small tensions in the Hubble constant (H0) values when compared to local measurements. The analysis suggests an H0 of approximately 69 km/s/Mpc, which slightly diverges from higher local measurements around 73 km/s/Mpc. The paper also suggests slight discrepancies in the growth rate of structures, which could suggest either a need for more sophisticated modeling or potential physics beyond ΛCDM.

Implications and Theoretical Interpretations

The results imply a consistent picture with the ΛCDM model but indicate potential areas where discrepancies could point to new physics. The slight differences in H0 and σ8 imply either complex systematic errors in data interpretation or the necessity for model extensions, such as evolving dark energy models or modified gravity theories.

Future Directions

The conclusions drawn from this analysis chart a course for future research, advocating for enhanced cross-correlation of cosmological data and refining systematics in measurement techniques. The integration of next-generation data from upcoming surveys, such as the Euclid and Nancy Grace Roman Space Telescope, promises to enhance constraints on Ων and the nature of dark energy. The continuation of such multi-probe approaches will not only fine-tune existing parameters but also potentially unveil new insights into fundamental physics.

In summary, this research provides a cogent synthesis of current cosmological data sets, offering precise constraints while also acknowledging deviations that could herald new theoretical developments or necessitate more intricate analyses of underlying data systemics.