Dark Energy Survey Year 3 results: cosmological constraints from the analysis of cosmic shear in harmonic space

Understand

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.