#### Our year 3 cosmology analysis of galaxy clustering and gravitational lensing is a massive effort from more than a hundred scientists. There will be 29 interconnected papers in all, with the main cosmology analysis at the bottom of the page.

#### Currently, 7 of the 29 papers have been released. Check them out!

#### More to come soon!

For questions, you can email lead authors, or thedarkenergysurvey@gmail.com

For a public overview of the goals of this analysis, check out these two DArchives discussing our year 1 cosmology analysis.

## Catalogs

**Dark Energy Survey Year 3 Results: Photometric Data Set for Cosmology**

Authors: I. Sevilla-Noarbe (nsevilla@gmail.com), K. Bechtol (kbechtol@wisc.edu), M. Carrasco Kind, et al.

We describe the Dark Energy Survey (DES) photometric data set assembled from the first three years of science operations to support DES Year 3 cosmology analyses, and provide usage notes aimed at the broad astrophysics community. This Y3 “GOLD” catalog comprises nearly 5000 deg2 of grizY imaging in the south Galactic cap, including nearly 390 million objects, with depth reaching S/N∼10 for extended objects up to i ∼ 23.0.

**Figure:** *Footprint of the DES Y3 Gold data (red) with DES Y1 (green) and SV (purple) overlaid.*

**Dark Energy Survey Year 3 Results: Weak Lensing Shape Catalogue**

Authors: M. Gatti (mgatti@ifae.es), E. Sheldon (erin.sheldon@gmail.com), A. Amon, M. Becker, M. Troxel, A. Choi, C. Doux, N. MacCrann, A. Navarro Alsina, I. Harrison, D. Gruen, G. Bernstein, M. Jarvis, L. F. Secco, A. Ferte, T. Shin, J. McCullough, R. P. Rollins, R. Chen, C. Chang, S. Pandey, I. Tutusaus, J. Prat, J. Elvin-Poole, C. Sanchez, et al.

We present and characterise the galaxy shape catalogue of DES Y3. Our self-calibrating shear measurement pipeline metacalibration builds and improves upon the pipeline used in the DES Year 1 analysis in several aspects. The final shape catalogue consists of 100,204,026 galaxies, measured in the riz bands, resulting in a weighted source number density of n_{eff}=5.59gal/arcmin^{2} and corresponding shape noise σ_{e}=0.261. We perform a battery of internal null tests on the catalogue, including tests on systematics related to the point-spread function (PSF) modelling, spurious catalogue B-mode signals, catalogue contamination, and galaxy properties to show that this catalog is ready for weak lensing cosmology.

**Figure:** *Effective density of weak lensing sources in the DES Y3 metacalibration shape catalog, across the full footprint*.

**Dark Energy Survey Year 3 Results: Point-Spread Function Modeling**

Authors: M. Jarvis (mjarvis@physics.upenn.edu), G. M. Bernstein, A. Amon, C. Davis, P. F. Léget, K. Bechtol, I. Harrison, M. Gatti, A. Roodman, et al.

We introduce a new software package for modeling the point-spread function (PSF) of astronomical images, called PIFF, which we apply to DES Y3. We describe the relevant details about the algorithms used by PIFF to model the PSF, including how the PSF model varies across the field of view. Diagnostic results show that the systematic errors from the PSF modeling are very small over the range of scales that are important for the DES Y3 weak lensing analysis. In particular, the systematic errors from the PSF modeling are significantly smaller than the corresponding results from the DES Y1 analysis. We also briefly describe some planned improvements to PIFF that we expect to further reduce the modeling errors in future analyses.

**Figure:** *The rho statistics are the principal diagnostic we use to establish the quality of the PSF model, since they contribute directly as an additive systematic error in the cosmic shear correlation functions. There are 5 statistics presented in these two figures, which are all demonstrated to be small enough not to significantly bias the DES Y3 cosmology analysis. Other statistics are presented in the paper.*

## Calibration

**Phenotypic redshifts with self-organizing maps: A novel method to characterize redshift distributions of source galaxies for weak lensing**

Authors: R. Buchs (romainbuchs@hotmail.com), C. P. Davis, D. Gruen, J. DeRose, A. Alarcon, G. M. Bernstein, C. Sanchéz, J. Myles, A. Roodman, et al.

Link to paper (arXiv) Link to paper (MNRAS)

We introduce a new method of linking information from spectroscopy or other high-quality redshift estimates to wide field weak lensing source samples via photometric multi-band deep fields. Using mock catalogs, we show that this significantly reduces sample variance in redshift calibration. This methodology is at the same time a key to being able to use spectroscopic information for calibration of DES photometric redshifts without dominant selection biases.

**Figure:*** Deep field multi-band photometry acts as an intermediary between redshift information and wide-field galaxy samples whose redshift distributions we calibrate.*

**Dark Energy Survey Year 3 Results: Redshift Calibration of the Weak Lensing Source Galaxies**

Authors: J. Myles, A. Alarcon, A. Amon, C. Sanchez, S. Everett, J. DeRose, J. McCullough, D. Gruen, G. Bernstein, M. Troxel, S. Dodelson, A. Campos, N. MacCrann, B. Yin, et al.

Paper: Coming soon

We present the derivation and validation of redshift distributions for the source galaxies used in the DES Y3 weak lensing measurements. As the first application of this method to data, we validate that the assumptions made apply to the DES Y3 weak lensing source galaxies and describe our treatment of systematic uncertainties. In a first for redshift analyses, we construct an ensemble of redshift distributions whose variation encodes all uncertainties and combines information from galaxy color, position correlation functions, and shear ratios.

**Figure:** *Ensemble of redshift distributions in four tomographic bins, as inferred from galaxy photometry. Each symbol shows the 95% credible interval of the probability of a galaxy in the weak lensing source sample and assigned to a given tomographic bin to have redshift z. The uncertainty on p(z) is due to biases in the secure redshifts used in the analysis, sample variance and shot noise in the galaxies in the DES deep fields, photometric calibration uncertainty for the DES deep fields, and the inherent uncertainty of the methods applied.*

## Theory

**Dark Energy Survey internal consistency tests of the joint cosmological probes analysis with posterior predictive distributions**

Author: C. Doux (cdoux@sas.upenn.edu), E. Baxter, P. Lemos, C. Chang, et al.

We present the methodology for testing the internal consistency of the Dark Energy Survey (DES) measurements of cosmic shear, galaxy-galaxy lensing and galaxy clustering. We focus on data space tests to best identify potential inconsistent subsets using posterior predictive distributions. When applied to DES Year 1 data, we find overall good consistency and a good fit to ΛCDM. We test consistency by splitting the data into different probes, redshift bins and scales and find a small tension between large- and small-scale measurements (at the <2σ level).

**Figure: ***Excerpt from Fig 2 of paper, comparing the posterior predictive distribution in blue and data in red for cosmic shear measurements when testing for 3x2pt goodness-of-fit (for both, we subtracted the best-fit and divided by the error for visualization)*.

**Blinding multi-probe cosmological experiments**

Authors: J. Muir (jlmuir@stanford.edu), G. Bernstein, D. Huterer, F. Elsner, E. Krause, A. Roodman, et al.

Link to paper (arXiv) Link to paper (MNRAS)

This paper introduces the transformation applied to DES Y3 galaxy clustering and weak lensing measurements in order to hide the cosmology results until decisions about how to conduct the analysis were finalized. The goal of this kind of concealment, known as blinding, is to protect the DES analysis from bias that might be unconsciously introduced if experimenters are looking at how analysis choices influence how the results compare to their expectations. DES is the first analysis to use this method, which works by altering the two-point correlation functions that are input to parameter estimation. This paper shows that, for simulated DES Y3 analyses, the transformation can successfully change the best-fit cosmological parameters while preserving the internal consistency of different parts of data.

**Figure: ***Effect of the blinding transformation on a simulated DES Y3 analysis.*

**Dark Energy Survey Year 3 Results: Optimizing the Lens Sample in Combined Galaxy Clustering and Galaxy-Galaxy Lensing Analysis**

Authors: A. Porredon (annam.porredon@gmail.com), M. Crocce, P. Fosalba, J. Elvin-Poole, I. Ferrero, E. Krause, X. Fang, T. Eifler, R. Cawthon, N. Weaverdyck, N. MacCrann, A. Carnero, et al.

We investigate potential gains in cosmological constraints from the combination of galaxy clustering and galaxy-galaxy lensing by optimizing the lens galaxy sample selection, using information from DES Y3. We explore easily reproducible selections based on magnitude cuts in i-band as a function of (photometric) redshift, zphot, and look to balance number density vs. photometric accuracy. Our optimal selection, the MAGLIM sample, satisfies i < 4 zphot + 18 and has ∼ 3.5 times more galaxies than our reference sample, REDMAGIC. Assuming a wCDM model and equivalent scale cuts for nonlinear effects, it leads to gains of 16% in σ8, 10% in Ωm, and 12% in w. In ΛCDM we find an improvement of 19% and 27% on σ8 and Ωm, respectively.

**Figure:** *ΛCDM constraints from the combination of galaxy clustering and galaxy-galaxy lensing using the REDMAGIC (red) and MAGLIM (blue) samples as lenses. The MAGLIM constraints are tighter by 27% on Ωm, and 11% on S8 compared to REDMAGIC.*