This AAS 245 Splinter Meeting will review Dark Energy Survey (DES) cosmology results in the broader context of other surveys, current and future, particularly the Vera C. Rubin Observatory’s Legacy Survey of Space and Time (LSST) and cosmology analysis by the Dark Energy Science Collaboration (DESC). The focus will be on constraints placed on cosmological parameters and whether the Lambda CDM model gives a consistent picture across experiments. The best constraints come from combinations of different experiments, and this Splinter Meeting will explore what can be expected in the coming years.

DES and DESC use wide-field and time-domain photometric surveys to produce a number of high-precision probes: supernova Type Ia detection and measurement; cluster abundance as a function of richness and redshift; galaxy-galaxy clustering; measurement of the weak-lensing shear field; the correlation between foreground galaxies and background tangential shear, and strongly lensed quasars and supernovae.

Because the signals are weak, the measurements need to be made with extreme precision so that systematics do not dominate the statistical precision. A large ongoing effort is developing methods to identify and mitigate systematic biases in the measurements and the analysis. Inconsistencies between probes (tensions) could either indicate the adopted cosmological model is incomplete, or that there is an unrecognized systematic still present in the analysis. In this AAS 245 Splinter Meeting, we will highlight some of the methods and results from DES, and lessons learned as we prepare for upcoming DESC analyses.

Tuesday, January 14, 2025 | 1:00 PM ET – 3:00 PM ET
Chesapeake C, Gaylord National Resort & Convention Center
Chairs: Richard Kron (DES), Gautham Narayan (DESC)

Speakers, Titles and Abstracts are provided below.
Slides and recordings of presentations will be made available shortly after the session.

DES is releasing a final “Gold” set of catalogs and maps that support cosmological analyses and more. Y6 Gold is based on Data Release 2 and adds value in several ways, including new and better object morphological classification compared to Y3 Gold; increased depth and photometric uniformity; refined and extended maps of survey conditions and foregrounds; and enhancements in photometric redshift estimates, especially for z ~ 1.
[Slides]

Cosmological analyses require accurate measurements of object properties and a robust characterization of the image processing pipelines. We present a synthetic dataset of 5000 deg^2 of the DES footprint, that calibrates our galaxy measurements at the sub-percent level while accounting for all complexities in the image data/processing. We show how this approach enables the robustness of all science analyses derived from this data, and highlight how it can be leveraged for analyses of upcoming photometric surveys.
[Slides]

The point-spread function (PSF) is a key ingredient for weak lensing analyses and a potential source of significant systematic bias in the cosmological results. In this talk, I will explain the key improvements made in the PSF characterization for the Dark Energy Survey Year 6 analysis, which result in negligible bias in the cosmological parameter inference. I will also discuss ongoing and future improvements to our PSF modeling software, PIFF, in light of Rubin Observatory’s upcoming Legacy Survey of Space and Time.
[Slides]

Extracting cosmological insights from noisy, distorted galaxy images presents significant challenges, with biased measurements posing a major concern. To overcome this, shear measurement methods must be carefully designed to mitigate systematic errors while maintaining statistical rigor. Metadetection, BFD, and AnaCal exemplify innovative approaches that address these challenges, paving the way for accurate analysis of billions of galaxy shapes with the next generation of large-scale surveys.
[Slides]

The DES 3x2pt analysis relied on robust redshift calibration, achieved through the combination of complementary techniques: self-organizing maps (SOMPZ), clustering redshifts, and shear ratios. I will discuss the successes and challenges of these methods, including how we addressed systematic uncertainties and developed efficient sampling strategies for cosmological inference. These achievements provide valuable insights for improving redshift calibration in next-generation surveys.
[Slides]

In this talk, I will detail some of the key analysis improvements from the final DES supernova analysis comprised of ~1600 photometrically classified SNe which have allowed us to make the best SNIa constraints on the dark energy equation of state parameter to date. I will discuss how these developments are informing current efforts underway in preparation for the next generation of surveys for supernova cosmology, specifically with Rubin LSST and the Roman Space Telescope.
[Slides]

The Strong Lensing Simulation (SLSim) pipeline generates realistic simulations of strong lensing systems, including galaxy-galaxy lenses, lensed transients, and cluster-scale lenses, tailored for Rubin and adaptable to Roman. It produces population-level catalogs, realistic images, and time-series imaging for transients, supporting lens finding challenges, observational preparations, and cosmological analysis. I will also discuss ongoing efforts to prepare for strong lensing science with LSST, building on these capabilities.
[Slides]

Galaxy clusters are powerful probes of cosmological models, and an essential component of the cosmology analysis plan of DES, and the upcoming Legacy Survey of Space and Time (LSST) at Vera Rubin Observatory. In this talk, I will briefly overview the methods and results from DES on galaxy cluster analysis, and then discuss how these analyses have informed preparation for LSST-based cluster analysis within the Dark Energy Science Collaboration.
[Slides]

Stage-III dark energy experiments have made incredible strides in the study of dark energy. Thanks to advances such as establishing the so-called 3x2pt technique, these experiments have opened new questions in the current cosmological paradigm. With its incredible statistical power, Rubin’s LSST will further take advantage of these techniques, but the importance of previously undetectable systematic effects will increase. In this talk we will present the preparations that DESC is making towards year 1 analyses and beyond, the challenges that Rubin and other experiments will face for their 3x2pt analyses, and how the combination of Stage IV data will help to solve some of these challenges.
[Slides]

In this talk I will discuss plans for photometric redshift (photo-z) estimation with the Vera Rubin Observatory’s Legacy Survey of Space and Time (LSST), including methodological advancements that continue from and branch off in new directions from DES. I will also discuss ongoing work using data from the science validation surveys conducted with Rubin’s Commissioning Camera (ComCam), and the potential for high-redshift cosmology using Lyman-break galaxies detected by LSST.
[Slides]

Although dark matter makes up ~85% of the matter in our Universe, we have not yet detected it in laboratory settings and its nature is not yet fully understood. However, observations of the smallest and faintest substructures in the local Universe, such as ultra-faint dwarf galaxies and stellar streams, from wide-field photometric surveys continue to provide key insights into the distribution and behavior of dark matter. In this talk, I will discuss how we have used Dark Energy Survey (DES) and DECam observations of local-volume satellites and stellar streams to further our understanding. In particular, how we constrain dark matter microphysics through the low-mass end of the galaxy-halo connection and probe its distribution at many scales in our Galaxy. Additionally, I will describe our plans within the Dark Energy Science Collaboration (DESC) to build upon our efforts in DES and use the Legacy Survey of Space and Time (LSST) data to infer even more about the nature of dark matter.
[Slides]

Funding for the DES Project has been provided by the U.S. Department of Energy, the U.S. National Science Foundation, the Ministry of Science and Education of Spain, the Science and Technology Facilities Council of the United Kingdom, the Higher Education Funding Council for England, the National Center for Supercomputing Applications at the University of Illinois at Urbana-Champaign, the Kavli Institute of Cosmological Physics at the University of Chicago, Financiadora de Estudos e Projetos, Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro, Conselho Nacional de Desenvolvimento Científico e Tecnológico and the Ministério da Ciência e Tecnologia and the Collaborating Institutions in the Dark Energy Survey.

The Dark Energy Science Collaboration (DESC) acknowledges ongoing support from the Institut National de Physique Nuclèaire et de Physique des Particules in France; the Science & Technology Facilities Council in the United Kingdom; and the Department of Energy, the National Science Foundation, and the LSST Discovery Alliance in the United States. DESC uses resources of the IN2P3 Computing Center (CC-IN2P3 – Lyon/Villeurbanne – France) funded by the Centre National de la Recherche Scientifique; the National Energy Research Scientific Computing Center, a DOE Office of Science User Facility supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC02-05CH11231; STFC DiRAC HPC Facilities, funded by UK BEIS National E-infrastructure capital grants; and the UK particle physics grid, supported by the GridPP Collaboration.