Session ID 232, Final Cosmological Constraints from the Dark Energy Survey
Tuesday, January 6, 2026, 1:00 – 2:30 pm
Phoenix Convention Center 126 C
https://submissions.mirasmart.com/AAS247/Itinerary/EventDetail.aspx?evt=108
About This Meeting:
The Dark Energy Survey (DES) collected images over 2013 – 2019 with the Dark Energy Camera on the Blanco Telescope at NOIRLab’s Cerro Tololo Interamerican Observatory. Cosmology results have been reported from the first year (Y1) and the first three years (Y3), and we are now presenting the constraints on cosmological parameters from all 6 years (Y6). DES was conceived to use four principal probes of geometry and the growth of structure: weak lensing, galaxy clustering, Type Ia supernovae, and the abundance of rich clusters of galaxies. In this Splinter Meeting, we focus on 1) the combination of cosmic shear, galaxy-galaxy lensing, and galaxy clustering; 2) the status of the Type Ia supernova calibration; and 3) constraints on extensions to the LambdaCDM model. We include overview remarks and pointers to some non-cosmological DES achievements.
Presenters:
Chihway Chang & Michael Troxel – Introduction to and Reflections on the Dark Energy Survey
Masaya Yamamoto – The Legacy Cosmological Constraints from Weak Lensing and Galaxy Clustering in DES
The Dark Energy Survey provides a rich dataset to explore the large-scale structure of the Universe through the effect of weak gravitational lensing and galaxy clustering. In order to extract unbiased cosmological information from the dataset, however, one requires robust analyses throughout the pixel-to-cosmology pipeline, such as measuring galaxy shapes and fluxes from images and modeling astrophysics accurately. In this talk, I will present the path we took, challenges we faced, and our legacy cosmology results using the combination of weak lensing and galaxy clustering.
Brodie Popovic – Improved Cosmological Constraints from Type Ia Supernovae
We present improved cosmological constraints from a re-analysis of the Dark Energy Survey 5-year sample of Type Ia supernovae (DES-SN5YR). This re-analysis includes an improved photometric cross-calibration, recent white dwarf observations to cross-calibrate between DES and low redshift surveys, retraining the SALT3 light curve model and fixing a numerical approximation in the host galaxy colour law. Our fully recalibrated sample, which we call DES-Dovekie, comprises ~1600 likely Type Ia SNe from DES and ~200 low-redshift SNe from other surveys. With DES-Dovekie, we obtain in Flat CDM which changes by -0.022 compared to DES-SN5YR. Combining DES-Dovekie with CMB data from Planck, ACT and SPT and the DESI DR2 measurements in a Flat CDM cosmology, we find . Our results hold a significance of , reduced from for DES-SN5YR, to reject the null hypothesis that the data are compatible with the cosmological constant. This significance is equivalent to a Bayesian model preference odds of approximately 5:1 in favour of the Flat CDM model. Using generally accepted thresholds for model preference, our updated data exhibits only a weak preference for evolving dark energy.
Sujeong Lee – Constraints on Extensions to ΛCDM from the Dark Energy Survey
Recent cosmological observations have shown intriguing hints of time-varying dark energy, suggesting possible cracks in the standard ΛCDM cosmological model. In this talk, I will present independent constraints on extensions to ΛCDM using the complete six-year Dark Energy Survey dataset, focusing on time-varying dark energy and modifications to gravity. Building on the 3×2pt analysis of weak lensing and galaxy clustering presented earlier in this session, I will describe our validation framework using simulated data vectors, discuss the modeling challenges that arise when extending beyond ΛCDM, and present our final results both from DES alone and in combination with external probes.
Richard Kron – Beyond Dark Energy: Astrophysics with DES
The combination of sky area, depth, cadence, bandpasses, photometric precision, and control of the point-spread function enables many kinds of investigations with DES data beyond constraints on dark energy. This talk will illustrate how DES has contributed to astrophysics with a small number of examples: outer Solar System, stellar streams, and unusual optical transients.