We present high signal-to-noise measurements of three-point shear correlations and the third moment of the mass aperture statistic using the first 3 years of data from the Dark Energy Survey. We ...additionally obtain the first measurements of the configuration and scale dependence of the four three-point shear correlations which carry cosmological information. With the third-order mass aperture statistic, we present tomographic measurements over angular scales of 4 to 60 arcminutes with a combined statistical significance of 15.0\(\sigma\). Using the tomographic information and measuring also the second-order mass aperture, we additionally obtain a skewness parameter and its redshift evolution. We find that the amplitudes and scale-dependence of these shear 3pt functions are in qualitative agreement with measurements in a mock galaxy catalog based on N-body simulations, indicating promise for including them in future cosmological analyses. We validate our measurements by showing that B-modes, parity-violating contributions and PSF modeling uncertainties are negligible, and determine that the measured signals are likely to be of astrophysical and gravitational origin.
We present cosmological constraints from the analysis of angular power spectra of cosmic shear maps based on data from the first three years of observations by the Dark Energy Survey (DES Y3). Our ...measurements are based on the pseudo-\(C_\ell\) method and offer a view complementary to that of the two-point correlation functions in real space, as the two estimators are known to compress and select Gaussian information in different ways, due to scale cuts. They may also be differently affected by systematic effects and theoretical uncertainties, such as baryons and intrinsic alignments (IA), making this analysis an important cross-check. In the context of \(\Lambda\)CDM, and using the same fiducial model as in the DES Y3 real space analysis, we find \({S_8 \equiv \sigma_8 \sqrt{\Omega_{\rm m}/0.3} = 0.793^{+0.038}_{-0.025}}\), which further improves to \({S_8 = 0.784\pm 0.026 }\) when including shear ratios. This constraint is within expected statistical fluctuations from the real space analysis, and in agreement with DES~Y3 analyses of non-Gaussian statistics, but favors a slightly higher value of \(S_8\), which reduces the tension with the Planck cosmic microwave background 2018 results from \(2.3\sigma\) in the real space analysis to \(1.5\sigma\) in this work. We explore less conservative IA models than the one adopted in our fiducial analysis, finding no clear preference for a more complex model. We also include small scales, using an increased Fourier mode cut-off up to \(k_{\rm max}={5}{h{\rm Mpc}^{-1}}\), which allows to constrain baryonic feedback while leaving cosmological constraints essentially unchanged. Finally, we present an approximate reconstruction of the linear matter power spectrum at present time, which is found to be about 20\% lower than predicted by Planck 2018, as reflected by the \(1.5\sigma\) lower \(S_8\) value.
We present reconstructed convergence maps, \textit{mass maps}, from the Dark Energy Survey (DES) third year (Y3) weak gravitational lensing data set. The mass maps are weighted projections of the ...density field (primarily dark matter) in the foreground of the observed galaxies. We use four reconstruction methods, each is a \textit{maximum a posteriori} estimate with a different model for the prior probability of the map: Kaiser-Squires, null B-mode prior, Gaussian prior, and a sparsity prior. All methods are implemented on the celestial sphere to accommodate the large sky coverage of the DES Y3 data. We compare the methods using realistic \(\Lambda\)CDM simulations with mock data that are closely matched to the DES Y3 data. We quantify the performance of the methods at the map level and then apply the reconstruction methods to the DES Y3 data, performing tests for systematic error effects. The maps are compared with optical foreground cosmic-web structures and are used to evaluate the lensing signal from cosmic-void profiles. The recovered dark matter map covers the largest sky fraction of any galaxy weak lensing map to date.
The Cold Spot is a puzzling large-scale feature in the Cosmic Microwave Background temperature maps and its origin has been subject to active debate. As an important foreground structure at low ...redshift, the Eridanus supervoid was recently detected, but it was subsequently determined that, assuming the standard \(\Lambda\)CDM model, only about 10-20\(\%\) of the observed temperature depression can be accounted for via its Integrated Sachs-Wolfe imprint. However, \(R\gtrsim100~h^{-1}\mathrm{Mpc}\) supervoids elsewhere in the sky have shown ISW imprints \(A_{\mathrm{ISW}}\approx5.2\pm1.6\) times stronger than expected from \(\Lambda\)CDM (\(A_{\mathrm{ISW}}=1\)), which warrants further inspection. Using the Year-3 redMaGiC catalogue of luminous red galaxies from the Dark Energy Survey, here we confirm the detection of the Eridanus supervoid as a significant under-density in the Cold Spot's direction at \(z<0.2\). We also show, with \(\mathrm{S/N}\gtrsim5\) significance, that the Eridanus supervoid appears as the most prominent large-scale under-density in the dark matter mass maps that we reconstructed from DES Year-3 gravitational lensing data. While we report no significant anomalies, an interesting aspect is that the amplitude of the lensing signal from the Eridanus supervoid at the Cold Spot centre is about \(30\%\) lower than expected from similar peaks found in N-body simulations based on the standard \(\Lambda\)CDM model with parameters \(\Omega_{\rm m} = 0.279\) and \(\sigma_8 = 0.82\). Overall, our results confirm the causal relation between these individually rare structures in the cosmic web and in the CMB, motivating more detailed future surveys in the Cold Spot region.
Peacebuilding is an interactive process that involves collaboration between peacebuilders and the victorious elites of a postwar society. While one of the most prominent assumptions of the ...peacebuilding literature asserts that the interests of domestic elites and peacebuilders coincide, Costly Democracy contends that they rarely align.It reveals that, while domestic elites in postwar societies may desire the resources that peacebuilders can bring, they are often less eager to adopt democracy, believing that democratic reforms may endanger their substantive interests. The book offers comparative analyses of recent cases of peacebuilding to deepen understanding of postwar democratization and better explain why peacebuilding missions often bring peace—but seldom democracy—to war-torn countries.
