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We use the Szekeres inhomogeneous cosmological models to study the growth of large-scale structure in the universe including nonzero spatial curvature and a cosmological constant. In particular, we use the Goode and Wainwright formulation of the solution, as in this form the models can be considered to represent exact nonlinear perturbations of an averaged background. We identify a density contrast in both classes I and II of the models, for which we derive growth evolution equations. By including $\Lambda$, the time evolution of the density contrast as well as kinematic quantities of interest can be tracked through the matter- and $\Lambda$-dominated cosmic eras up to the present and into the future. In class I, we consider a localized cosmic structure representing an overdensity neighboring a central void, surrounded by an almost Friedmann-Lemaître-Robertson-Walker background, while for class II, the exact perturbations exist globally. In various models of class I and class II, the growth rate is found to be stronger in the matter-dominated era than that of the standard lambda-cold dark matter ($\Lambda \mathrm{CDM}$) cosmology, and it is suppressed at later times due to the presence of the cosmological constant. We find that there are Szekeres models able to provide a growth history similar to that of $\Lambda \mathrm{CDM}$ while requiring less matter content and nonzero spatial curvature, which speaks to the importance of including the effects of large-scale inhomogeneities in analyzing the growth of large-scale structure. Using data for the growth factor $f$ from redshift space distortions and the Lyman-$\alpha$ forest, we obtain best fit parameters for class II models and compare their ability to match observations with $\Lambda \mathrm{CDM}$. We find that there is negligible difference between best fit Szekeres models with no priors and those for $\Lambda \mathrm{CDM}$, both including and excluding Lyman-$\alpha$ data. We also find that the standard growth index $\gamma$ parametrization cannot be applied in a simple way to the growth in Szekeres models, so a direct comparison of the function $f$ to the data is performed. We conclude that the Szekeres models can provide an exact framework for the analysis of large-scale growth data that includes inhomogeneities and allows for different interpretations of observations.

We cross-correlate galaxy weak lensing measurements from the Dark Energy Survey (DES) year-one data with a cosmic microwave background (CMB) weak lensing map derived from South Pole Telescope (SPT) and Planck data, with an effective overlapping area of $1289{\mathrm{deg}}^2$. With the combined measurements from four source galaxy redshift bins, we obtain a detection significance of $5.8\sigma$. We fit the amplitude of the correlation functions while fixing the cosmological parameters to a fiducial $\mathrm{\Lambda }\mathrm{CDM}$ model, finding $A=0.99\pm 0.17$. We additionally use the correlation function measurements to constrain shear calibration bias, obtaining constraints that are consistent with previous DES analyses. Finally, when performing a cosmological analysis under the $\mathrm{\Lambda }\mathrm{CDM}$ model, we obtain the marginalized constraints of ${\mathrm{\Omega }}_{\mathrm{m}}=0.261_{-0.051}^{+0.070}$ and $S_8\equiv {\sigma }_8\sqrt{{\mathrm{\Omega }}_{\mathrm{m}}/0.3}=0.660_{-0.100}^{+0.085}$. These measurements are used in a companion work that presents cosmological constraints from the joint analysis of two-point functions among galaxies, galaxy shears, and CMB lensing using DES, SPT, and Planck data.

Galaxy intrinsic alignments (IA) are a critical uncertainty for current and future weak lensing measurements. We describe a perturbative expansion of IA, analogous to the treatment of galaxy biasing. From an astrophysical perspective, this model includes the expected large-scale alignment mechanisms for galaxies that are pressure-supported (tidal alignment) and rotation-supported (tidal torquing) as well as the cross-correlation between the two. Alternatively, this expansion can be viewed as an effective model capturing all relevant effects up to the given order. We include terms up to second order in the density and tidal fields and calculate the resulting IA contributions to two-point statistics at one-loop order. For fiducial amplitudes of the IA parameters, we find the quadratic alignment and linear-quadratic cross terms can contribute order-unity corrections to the total intrinsic alignment signal at $k\sim 0.1h^{-1}\mathrm{Mpc}$, depending on the source redshift distribution. These contributions can lead to significant biases on inferred cosmological parameters in Stage IV photometric weak lensing surveys. We perform forecasts for an LSST-like survey, finding that use of the standard “nonlinear linear alignment” model for intrinsic alignments cannot remove these large parameter biases, even when allowing for a more general redshift dependence. The model presented here will allow for more accurate and flexible IA treatment in weak lensing and combined probes analyses, and an implementation is made available as part of the public FAST-PT code. The model also provides a more advanced framework for understanding the underlying IA processes and their relationship to fundamental physics.

We derive cosmological constraints from the probability distribution function (PDF) of evolved large-scale matter density fluctuations. We do this by splitting lines of sight by density based on their count of tracer galaxies, and by measuring both gravitational shear around and counts-in-cells in overdense and underdense lines of sight, in Dark Energy Survey (DES) First Year and Sloan Digital Sky Survey (SDSS) data. Our analysis uses a perturbation theory model [O. Friedrich et al., Phys. Rev. D 98, 023508 (2018)] and is validated using $N$-body simulation realizations and log-normal mocks. It allows us to constrain cosmology, bias and stochasticity of galaxies with respect to matter density and, in addition, the skewness of the matter density field. From a Bayesian model comparison, we find that the data weakly prefer a connection of galaxies and matter that is stochastic beyond Poisson fluctuations on $\le 20\mathrm{arcmin}$ angular smoothing scale. The two stochasticity models we fit yield DES constraints on the matter density ${\mathrm{\Omega }}_m=0.26_{-0.03}^{+0.04}$ and ${\mathrm{\Omega }}_m=0.28_{-0.04}^{+0.05}$ that are consistent with each other. These values also agree with the DES analysis of galaxy and shear two-point functions (3x2pt, DES Collaboration et al.) that only uses second moments of the PDF. Constraints on ${\sigma }_8$ are model dependent (${\sigma }_8=0.97_{-0.06}^{+0.07}$ and $0.80_{-0.07}^{+0.06}$ for the two stochasticity models), but consistent with each other and with the 3 x 2pt results if stochasticity is at the low end of the posterior range. As an additional test of gravity, counts and lensing in cells allow to compare the skewness $S_3$ of the matter density PDF to its $\mathrm{\Lambda }\mathrm{CDM}$ prediction. We find no evidence of excess skewness in any model or data set, with better than 25 per cent relative precision in the skewness estimate from DES alone.

We present density split statistics, a framework that studies lensing and counts-in-cells as a function of foreground galaxy density, thereby providing a large-scale measurement of both 2-point and 3-point statistics. Our method extends our earlier work on trough lensing and is summarized as follows: given a foreground (low redshift) population of galaxies, we divide the sky into subareas of equal size but distinct galaxy density. We then measure lensing around uniformly spaced points separately in each of these subareas, as well as counts-in-cells statistics (CiC). The lensing signals trace the matter density contrast around regions of fixed galaxy density. Through the CiC measurements this can be related to the density profile around regions of fixed matter density. Together, these measurements constitute a powerful probe of cosmology, the skewness of the density field and the connection of galaxies and matter. In this paper we show how to model both the density split lensing signal and CiC from basic ingredients: a non-linear power spectrum, clustering hierarchy coefficients from perturbation theory and a parametric model for galaxy bias and shot-noise. Using N-body simulations, we demonstrate that this model is sufficiently accurate for a cosmological analysis on year 1 data from the Dark Energy Survey.

We present constraints on extensions of the minimal cosmological models dominated by dark matter and dark energy, $\mathrm{\Lambda }\mathrm{CDM}$ and $w\mathrm{CDM}$, by using a combined analysis of galaxy clustering and weak gravitational lensing from the first-year data of the Dark Energy Survey (DES Y1) in combination with external data. We consider four extensions of the minimal dark energy-dominated scenarios: (1) nonzero curvature ${\mathrm{\Omega }}_k$, (2) number of relativistic species $N_{\mathrm{eff}}$ different from the standard value of 3.046, (3) time-varying equation-of-state of dark energy described by the parameters $w_0$ and $w_a$ (alternatively quoted by the values at the pivot redshift, $w_p$, and $w_a$), and (4) modified gravity described by the parameters ${\mu }_0$ and ${\mathrm{\Sigma }}_0$ that modify the metric potentials. We also consider external information from Planck cosmic microwave background measurements; baryon acoustic oscillation measurements from SDSS, 6dF, and BOSS; redshift-space distortion measurements from BOSS; and type Ia supernova information from the Pantheon compilation of datasets. Constraints on curvature and the number of relativistic species are dominated by the external data; when these are combined with DES Y1, we find ${\mathrm{\Omega }}_k=0.0020_{-0.0032}^{+0.0037}$ at the 68% confidence level, and the upper limit $N_{\mathrm{eff}}<3.28(3.55)$ at 68% (95%) confidence, assuming a hard prior $N_{\mathrm{eff}}>3.0$. For the time-varying equation-of-state, we find the pivot value $(w_p,w_a)=(-0.91_{-0.23}^{+0.19},-0.57_{-1.11}^{+0.93})$ at pivot redshift $z_p=0.27$ from DES alone, and $(w_p,w_a)=(-1.01_{-0.04}^{+0.04},-0.28_{-0.48}^{+0.37})$ at $z_p=0.20$ from DES Y1 combined with external data; in either case we find no evidence for the temporal variation of the equation of state. For modified gravity, we find the present-day value of the relevant parameters to be ${\mathrm{\Sigma }}_0=0.43_{-0.29}^{+0.28}$ from DES Y1 alone, and $({\mathrm{\Sigma }}_0,{\mu }_0)=(0.06_{-0.07}^{+0.08},-0.11_{-0.46}^{+0.42})$ from DES Y1 combined with external data. These modified-gravity constraints are consistent with predictions from general relativity.

We analyze Dark Energy Survey (DES) data to constrain a cosmological model where a subset of parameters—focusing on ${\mathrm{\Omega }}_m$—are split into versions associated with structure growth (e.g., ${\mathrm{\Omega }}_m^{\mathrm{grow}}$) and expansion history (e.g., ${\mathrm{\Omega }}_m^{\mathrm{geo}}$). Once the parameters have been specified for the $\mathrm{\Lambda }\mathrm{CDM}$ cosmological model, which includes general relativity as a theory of gravity, it uniquely predicts the evolution of both geometry (distances) and the growth of structure over cosmic time. Any inconsistency between measurements of geometry and growth could therefore indicate a breakdown of that model. Our growth-geometry split approach therefore serves both as a (largely) model-independent test for beyond-$\mathrm{\Lambda }\mathrm{CDM}$ physics, and as a means to characterize how DES observables provide cosmological information. We analyze the same multiprobe DES data as [Phys. Rev. Lett. 122, 171301 (2019)] : DES Year 1 (Y1) galaxy clustering and weak lensing, which are sensitive to both growth and geometry, as well as Y1 BAO and Y3 supernovae, which probe geometry. We additionally include external geometric information from BOSS DR12 BAO and a compressed Planck 2015 likelihood, and external growth information from BOSS DR12 RSD. We find no significant disagreement with ${\mathrm{\Omega }}_m^{\mathrm{grow}}={\mathrm{\Omega }}_m^{\mathrm{geo}}$. When DES and external data are analyzed separately, degeneracies with neutrino mass and intrinsic alignments limit our ability to measure ${\mathrm{\Omega }}_m^{\mathrm{grow}}$, but combining DES with external data allows us to constrain both growth and geometric quantities. We also consider a parametrization where we split both ${\mathrm{\Omega }}_m$ and $w$, but find that even our most constraining data combination is unable to separately constrain ${\mathrm{\Omega }}_m^{\mathrm{grow}}$ and $w^{\mathrm{grow}}$. Relative to $\mathrm{\Lambda }\mathrm{CDM}$, splitting growth and geometry weakens bounds on ${\sigma }_8$ but does not alter constraints on $h$.

This work is part of a series establishing the redshift framework for the $3\times 2\mathrm{pt}$ analysis of the Dark Energy Survey Year 6 (DES Y6). For DES Y6, photometric redshift distributions are estimated using self-organizing maps (SOMs), calibrated with spectroscopic and many-band photometric data. To overcome limitations from color-redshift degeneracies and incomplete spectroscopic coverage, we enhance this approach by incorporating clustering-based redshift constraints (clustering-z, or WZ) from angular cross-correlations with BOSS and eBOSS galaxies and eBOSS quasar samples. We define a WZ likelihood and apply importance sampling to a large ensemble of SOM-derived $n(z)$ realizations, selecting those consistent with the clustering measurements to produce a posterior sample for each lens and source bin. The analysis uses angular scales corresponding to 1.5–5 Mpc to optimize signal-to-noise ratio while mitigating modeling uncertainties and marginalizes over redshift-dependent galaxy bias and other systematics informed by the N-body simulation cardinal. While a sparser spectroscopic reference sample limits WZ constraining power at $z>1.1$, particularly for source bins, we demonstrate that combining SOM with WZ improves redshift accuracy and enhances the overall cosmological constraining power of DES Y6. We estimate an improvement in $S_8$ of approximately 10% for cosmic shear and $3\times 2\mathrm{pt}$ analysis, primarily due to the WZ calibration of the source samples.

We introduce here a cross-correlation term between CMB lensing and galaxy intrinsic alignment, noted here as $\varphi I$. This effect acts as a contaminant to the cross correlation between CMB lensing and galaxy lensing. The latter cross correlation has recently been detected for the first time, and measurements will greatly improve as the area of overlap between galaxy and CMB surveys increases and measurements of the CMB polarization become more significant. This will constitute a powerful probe for studying the structure and evolution of the universe. The magnitude of the $\varphi I$ term is found to be about 15% of the pure CMB lensing-galaxy lensing component and acts to reduce the magnitude of its measured spectrum. This offset in the spectrum will strongly impact its use for precision cosmological study if left unmitigated. We also propose here a method to calibrate this $\varphi I$ contamination through the use of a scaling relation that allows one to reduce the impact of $\varphi I$ by a factor of 20 or more in all redshift bins, which would reduce its magnitude down to detection limits in almost all cases. This will allow the full use of this probe for precision cosmology.

We study effects of inhomogeneities on distance measures in an exact relativistic Swiss-cheese model of the Universe, focusing on the distance modulus. The model has $\mathrm{\Lambda }\mathrm{CDM}$ background dynamics, and the “holes” are nonsymmetric structures described by the Szekeres metric. The Szekeres exact solution of Einstein’s equations, which is inhomogeneous and anisotropic, allows us to capture potentially relevant effects on light propagation due to nontrivial evolution of structures in an exact framework. Light beams traversing a single Szekeres structure in different ways can experience either magnification or demagnification, depending on the particular path. Consistent with expectations, we find a shift in the distance modulus $\mu$ to distant sources due to demagnification when the light beam travels primarily through the void regions of our model. Conversely, beams are magnified when they propagate mainly through the overdense regions of the structures, and we explore a small additional effect due to time evolution of the structures. We then study the probability distributions of $\mathrm{\Delta }\mu ={\mu }_{\mathrm{\Lambda }\text{CDM}}-{\mu }_{\mathrm{SC}}$ for sources at different redshifts in various Swiss-cheese constructions, where the light beams travel through a large number of randomly oriented Szekeres holes with random impact parameters. We find for $\mathrm{\Delta }\mu$ the dispersions $0.004\le {\sigma }_{\mathrm{\Delta }\mu }\le 0.008$ mag for sources with redshifts $1.0\le z\le 1.5$, which are smaller than the intrinsic dispersion of, for example, magnitudes of type Ia supernovae. The shapes of the distributions we obtain for our Swiss-cheese constructions are peculiar in the sense that they are not consistently skewed toward the demagnification side, as they are in analyses of lensing in cosmological simulations. Depending on the source redshift, the distributions for our models can be skewed to either the demagnification or the magnification side, reflecting a limitation of these constructions. This could be the result of requiring the continuity of Einstein’s equations throughout the overall spacetime patchwork, which imposes the condition that compensating overdense shells must accompany the underdense void regions in the holes. The possibility to explore other uses of these constructions that could circumvent this limitation and lead to different statistics remains open.

We present cosmological constraints from the abundance of galaxy clusters selected via the thermal Sunyaev-Zel’dovich (SZ) effect in South Pole Telescope (SPT) data with a simultaneous mass calibration using weak gravitational lensing data from the Dark Energy Survey (DES) and the Hubble Space Telescope (HST). The cluster sample is constructed from the combined SPT-SZ, SPTpol ECS, and SPTpol 500d surveys, and comprises 1,005 confirmed clusters in the redshift range 0.25–1.78 over a total sky area of $5200{\mathrm{deg}}^2$. We use DES Year 3 weak-lensing data for 688 clusters with redshifts $z<0.95$ and HST weak-lensing data for 39 clusters with $0.6<z<1.7$. The weak-lensing measurements enable robust mass measurements of sample clusters and allow us to empirically constrain the SZ observable-mass relation without having to make strong assumptions about, e.g., the hydrodynamical state of the clusters. For a flat $\mathrm{\Lambda }\mathrm{CDM}$ cosmology, and marginalizing over the sum of massive neutrinos, we measure ${\mathrm{\Omega }}_{\mathrm{m}}=0.286\pm 0.032$, ${\sigma }_8=0.817\pm 0.026$, and the parameter combination ${\sigma }_8({\mathrm{\Omega }}_{\mathrm{m}}/0.3{)}^{0.25}=0.805\pm 0.016$. Our measurement of $S_8\equiv {\sigma }_8\sqrt{{\mathrm{\Omega }}_{\mathrm{m}}/0.3}=0.795\pm 0.029$ and the constraint from Planck CMB anisotropies (2018 TT, TE, $\mathrm{EE}+\mathrm{lowE}$) differ by $1.1\sigma$. In combination with that Planck dataset, we place a 95% upper limit on the sum of neutrino masses $\sum m_{\nu }<0.18\mathrm{eV}$. When additionally allowing the dark energy equation of state parameter $w$ to vary, we obtain $w=-1.45\pm 0.31$ from our cluster-based analysis. In combination with Planck data, we measure $w=-1.34_{-0.15}^{+0.22}$, or a $2.2\sigma$ difference with a cosmological constant. We use the cluster abundance to measure ${\sigma }_8$ in five redshift bins between 0.25 and 1.8, and we find the results to be consistent with structure growth as predicted by the $\mathrm{\Lambda }\mathrm{CDM}$ model fit to Planck primary CMB data.

We present the first constraints on cosmology from the Dark Energy Survey (DES), using weak lensing measurements from the preliminary Science Verification (SV) data. We use 139 square degrees of SV data, which is less than 3% of the full DES survey area. Using cosmic shear 2-point measurements over three redshift bins we find ${\sigma }_8({\mathrm{\Omega }}_{\mathrm{m}}/0.3{)}^{0.5}=0.81\pm 0.06$ (68% confidence), after marginalizing over 7 systematics parameters and 3 other cosmological parameters. We examine the robustness of our results to the choice of data vector and systematics assumed, and find them to be stable. About 20% of our error bar comes from marginalizing over shear and photometric redshift calibration uncertainties. The current state-of-the-art cosmic shear measurements from CFHTLenS are mildly discrepant with the cosmological constraints from Planck CMB data; our results are consistent with both data sets. Our uncertainties are $\sim 30\%$ larger than those from CFHTLenS when we carry out a comparable analysis of the two data sets, which we attribute largely to the lower number density of our shear catalogue. We investigate constraints on dark energy and find that, with this small fraction of the full survey, the DES SV constraints make negligible impact on the Planck constraints. The moderate disagreement between the CFHTLenS and Planck values of ${\sigma }_8({\mathrm{\Omega }}_{\mathrm{m}}/0.3{)}^{0.5}$ is present regardless of the value of $w$.

The combination of multiple observational probes has long been advocated as a powerful technique to constrain cosmological parameters, in particular dark energy. The Dark Energy Survey has measured 207 spectroscopically confirmed type Ia supernova light curves, the baryon acoustic oscillation feature, weak gravitational lensing, and galaxy clustering. Here we present combined results from these probes, deriving constraints on the equation of state, $w$, of dark energy and its energy density in the Universe. Independently of other experiments, such as those that measure the cosmic microwave background, the probes from this single photometric survey rule out a Universe with no dark energy, finding $w=-0.80_{-0.11}^{+0.09}$. The geometry is shown to be consistent with a spatially flat Universe, and we obtain a constraint on the baryon density of ${\mathrm{\Omega }}_b=0.069_{-0.012}^{+0.009}$ that is independent of early Universe measurements. These results demonstrate the potential power of large multiprobe photometric surveys and pave the way for order of magnitude advances in our constraints on properties of dark energy and cosmology over the next decade.

We perform a joint analysis of the counts and weak lensing signal of redMaPPer clusters selected from the Dark Energy Survey (DES) Year 1 dataset. Our analysis uses the same shear and source photometric redshifts estimates as were used in the DES combined probes analysis. Our analysis results in surprisingly low values for $S_8={\sigma }_8({\mathrm{\Omega }}_{\mathrm{m}}/0.3{)}^{0.5}=0.65\pm 0.04$, driven by a low matter density parameter, ${\mathrm{\Omega }}_{\mathrm{m}}=0.179_{-0.038}^{+0.031}$, with ${\sigma }_8-{\mathrm{\Omega }}_{\mathrm{m}}$ posteriors in $2.4\sigma$ tension with the DES Y1 3x2pt results, and in $5.6\sigma$ with the Planck CMB analysis. These results include the impact of post-unblinding changes to the analysis, which did not improve the level of consistency with other data sets compared to the results obtained at the unblinding. The fact that multiple cosmological probes (supernovae, baryon acoustic oscillations, cosmic shear, galaxy clustering and CMB anisotropies), and other galaxy cluster analyses all favor significantly higher matter densities suggests the presence of systematic errors in the data or an incomplete modeling of the relevant physics. Cross checks with x-ray and microwave data, as well as independent constraints on the observable-mass relation from Sunyaev-Zeldovich selected clusters, suggest that the discrepancy resides in our modeling of the weak lensing signal rather than the cluster abundance. Repeating our analysis using a higher richness threshold ($\lambda \ge 30$) significantly reduces the tension with other probes, and points to one or more richness-dependent effects not captured by our model.

We study a phenomenological class of models where dark matter converts to dark radiation in the low redshift epoch. This class of models, dubbed DMDR, characterizes the evolution of comoving dark-matter density with two extra parameters, and may be able to help alleviate the observed discrepancies between early and late-time probes of the Universe. We investigate how the conversion affects key cosmological observables such as the cosmic microwave background (CMB) temperature and matter power spectra. Combining 3x2pt data from Year 1 of the Dark Energy Survey, Planck-2018 CMB temperature and polarization data, supernovae (SN) Type Ia data from Pantheon, and baryon acoustic oscillation (BAO) data from BOSS DR12, MGS and 6dFGS, we place new constraints on the amount of dark matter that has converted to dark radiation and the rate of this conversion. The fraction of the dark matter that has converted since the beginning of the Universe in units of the current amount of dark matter, $\zeta$, is constrained at 68% confidence level to be $<0.32$ for DES-Y1 3x2pt data, $<0.030$ for $\mathrm{CMB}+\mathrm{SN}+\mathrm{BAO}$ data, and $<0.037$ for the combined dataset. The probability that the DES and CMB+SN+BAO datasets are concordant increases from 4% for the $\mathrm{\Lambda }\mathrm{CDM}$ model to 8% (less tension) for DMDR. The tension in $S_8={\sigma }_8\sqrt{{\mathrm{\Omega }}_m/0.3}$ between DES-Y1 3x2pt and $\mathrm{CMB}+\mathrm{SN}+\mathrm{BAO}$ is slightly reduced from $2.3\sigma$ to $1.9\sigma$. We find no reduction in the Hubble tension when the combined data is compared to distance-ladder measurements in the DMDR model. The maximum-posterior goodness-of-fit statistics of DMDR and $\mathrm{\Lambda }\mathrm{CDM}$ model are comparable, indicating no preference for the DMDR cosmology over $\mathrm{\Lambda }\mathrm{CDM}$.

In this work, we derive and calibrate the redshift distribution of the MagLim++ lens galaxy sample used in the Dark Energy Survey Year 6 (DES Y6) $3\times 2\mathrm{pt}$ cosmology analysis. The $3\times 2\mathrm{pt}$ analysis combines galaxy clustering from the lens galaxy sample and weak gravitational lensing. The redshift distributions are inferred using the SOMPZ method—a self-organizing map framework that combines deep-field multiband photometry, wide-field data, and a synthetic source injection (balrog) catalog. Key improvements over the DES Year 3 (Y3) calibration include a noise-weighted SOM metric, an expanded balrog catalog, and an improved scheme for propagating systematic uncertainties, which allows us to generate $\mathrm{O}({10}^8)$ redshift realizations that collectively span the dominant sources of uncertainty. These realizations are then combined with independent clustering-redshift measurements via importance sampling. The resulting calibration achieves typical uncertainties on the mean redshift of 1%–2%, corresponding to a 20%–30% average reduction relative to DES Y3. We compress the $n(z)$ uncertainties into a small number of orthogonal modes for use in cosmological inference. Marginalizing over these modes leads to only a minor degradation in cosmological constraints. This analysis establishes the MagLim++ sample as a robust lens sample for precision cosmology with DES Y6 and provides a scalable framework for future surveys.

The Dark Energy Survey (DES) recently released the final results of its two principal probes of the expansion history: Type Ia supernovae (SNe) and baryonic acoustic oscillations (BAO). In this paper, we explore the cosmological implications of these data in combination with external cosmic microwave background (CMB), big bang nucleosynthesis (BBN), and age-of-the-Universe information. The BAO measurement, which is $\sim 2\sigma$ away from Planck ’s $\mathrm{\Lambda }\mathrm{CDM}$ predictions, pushes for low values of ${\mathrm{\Omega }}_{\mathrm{m}}$ compared to Planck, in contrast to SN which prefers a higher value than Planck. We identify several tensions among datasets in the $\mathrm{\Lambda }\mathrm{CDM}$ model that cannot be resolved by including either curvature ($k\mathrm{\Lambda }\mathrm{CDM}$) or a constant dark energy equation of state ($w\mathrm{CDM}$). By combining $\mathrm{BAO}+\mathrm{SN}+\mathrm{CMB}$ despite these mild tensions, we obtain ${\mathrm{\Omega }}_k=-{5.5}_{-4.2}^{+4.6}\times {10}^{-3}$ in $k\mathrm{\Lambda }\mathrm{CDM}$, and $w=-0.948_{-0.027}^{+0.028}$ in $w\mathrm{CDM}$. In $w\mathrm{CDM}$, BAO and SN push again in different directions of parameter space, favoring, respectively, $w<-1$ and $w>-1$. If we open the parameter space to $w_0{w}_a\mathrm{CDM}$ [where the equation of state of dark energy varies as $w(a)=w_0+(1-a)w_a$], all the datasets are mutually more compatible, and we find concordance in the $[w_0>-1,w_a<0]$ quadrant, with BAO pushing for $w_a<0$ and SN for $[w_0>-1,w_a<0]$. For DES BAO and SN in combination with Planck -CMB, we find a $3.2\sigma$ deviation from $\mathrm{\Lambda }\mathrm{CDM}$, with $w_0=-0.673_{-0.097}^{+0.098}$, $w_a=-1.37_{-0.50}^{+0.51}$, a Hubble constant of $H_0=67.81_{-0.86}^{+0.96}\mathrm{km}{\mathrm{s}}^{-1}{\mathrm{Mpc}}^{-1}$, and an abundance of matter of ${\mathrm{\Omega }}_{\mathrm{m}}=0.3109_{-0.0099}^{+0.0086}$. For the combination of all the background cosmological probes considered (including CMB’s angular acoustic scale ${\theta }_{\star }$), we still find a deviation of $2.8\sigma$ from $\mathrm{\Lambda }\mathrm{CDM}$ in the $w_0-w_a$ plane. Assuming a minimal neutrino mass, this work provides tentative evidence for non-$\mathrm{\Lambda }\mathrm{CDM}$ physics, which is consistent with recent claims in support of evolving dark energy, or a source of unknown systematics.

We present constraints on models of cosmology and astrophysics using cosmic shear data vectors from three datasets: the northern and southern Galactic cap of the Dark Energy Camera All Data Everywhere (DECADE) project, and the Dark Energy Survey (DES) Year 3. These data vectors combined consist of 270 million galaxies spread across $13,000{\mathrm{deg}}^2$ of the sky. We first extract constraints for $\mathrm{\Lambda }\mathrm{CDM}$ cosmology and find $S_8=0.805_{-0.019}^{+0.019}$ and ${\mathrm{\Omega }}_{\mathrm{m}}=0.262_{-0.036}^{+0.023}$, which is consistent within $1.9\sigma$ of constraints from the Planck satellite. Extending our analysis to dynamical dark energy models shows that lensing provides some (but still minor) improvements to existing constraints from supernovae and baryon acoustic oscillations. Finally, we study six different models for the impact of baryons on the matter power spectrum. We show the different models provide consistent constraints on baryon suppression, and associated cosmology, once the astrophysical priors are sufficiently wide. Current scale-cut approaches for mitigating baryon contamination result in a residual bias of $\approx 0.3\sigma$ in the $S_8,{\mathrm{\Omega }}_{\mathrm{m}}$ posterior. Using all scales with dedicated baryon modeling leads to negligible improvement as the new information is used solely to self-calibrate the baryon model on small scales. Additional nonlensing datasets, and/or calibrations of the baryon model, will be required to access the full statistical power of the lensing measurements. The combined dataset in this work represents the largest lensing dataset to date (most galaxies, largest area) and provides an apt testing ground for analyses of upcoming datasets from stage IV surveys. The DECADE shear catalogs, data vectors, likelihoods, etc. are made publicly available.

Optical imaging surveys measure both the galaxy density and the gravitational lensing-induced shear fields across the sky. Recently, the Dark Energy Survey (DES) Collaboration used a joint fit to two-point correlations between these observables to place tight constraints on cosmology (T. M. C. Abbott et al. (Dark Energy Survey Collaboration), Phys. Rev. D 98, 043526 (2018)). In this work, we develop the methodology to extend the DES Year 1 joint probes analysis to include cross-correlations of the optical survey observables with gravitational lensing of the cosmic microwave background as measured by the South Pole Telescope (SPT) and Planck. Using simulated analyses, we show how the resulting set of five two-point functions increases the robustness of the cosmological constraints to systematic errors in galaxy lensing shear calibration. Additionally, we show that contamination of the SPT+Planck cosmic microwave background lensing map by the thermal Sunyaev-Zel’dovich effect is a potentially large source of systematic error for two-point function analyses but show that it can be reduced to acceptable levels in our analysis by masking clusters of galaxies and imposing angular scale cuts on the two-point functions. The methodology developed here will be applied to the analysis of data from the DES, the SPT, and Planck in a companion work.