The DES project

Ramon Miquel


Since 2005, a group at IFAE, together with a group at ICE (Institut de Ciències de l’Espai), and another at CIEMAT (Centro de Investigaciones Energéticas, Medio Ambientales y Tecnológicas) and Universidad Autónoma de Madrid (UAM), collaborates in the DES (Dark Energy Survey) international project, led by Fermilab (USA).

INTRODUCTION

The Dark Energy Survey started in 2013 and is the largest photometric galaxy survey ever, having, in six years, imaged 5000 sq. deg. (a full octant of the sky) in five optical and near-infrared bands (grizY) to unprecedented depth (iAB ~ 24), and measuring the position on the sky, distance and shape of more than 200 million galaxies up to redshift z ~ 1.4. IFAE is a founding member of the collaboration, and designed and produced a large fraction of the readout electronics of the DES camera, DECam. The survey has as its main goal to unveil the nature of the mysterious dark-energy component of the universe that powers its current accelerated expansion.

2024 ACTIVITIES

In 2021, DES presented the cosmological results from the data taken in the first three years of observations (DES-Y3), including more than 100 million distant galaxies. The next major step will be the publication of the results of the cosmological analyses of the whole six years of observations (DES-Y6), now expected in summer 2025. During 2024, the analysis of the full dataset proceeded at an increased pace. IFAE researchers co-led two of the main DES science working groups: the large-scale structure (LSS) group and the redshift group. Within the LSS group, the final results containing the Baryon Acoustic Oscillations (BAO) measurements with the full DES data sample were published in 2024 [T.M.C. Abbott et al. (DES Collaboration) 2024, PRD 110, 6], with an IFAE researcher as its corresponding author (Fig. 1).

Image
Figure 1: Ratio between the measured angular BAO scale at different redshifts for several galaxy surveys and the prediction from the cosmological parameters determined by Planck, assuming ΛCDM. A series of measurements by SDSS are included, as well as the DES-Y1 and -Y3 results. The DES-Y6 measurement is shown with an orange star. This plot represented the most updated angular BAO distance ladder at the time of publication.

Following on a line of research the group started back in 2015, an IFAE PhD student led a paper in 2024 presenting the measurements of the cross-correlations between the maps with the positions of DES-Y3 cosmic voids and superclusters and the CMB lensing maps from the Planck satellite [U. Demirbozan et al. (DES Collaboration) 2024, MNRAS 534, 2328], using a novel void finder algorithm. The analysis found good agreement between the observations and the predictions from simulations that assume the standard ΛCDM cosmology, contrary to some earlier indications from cross-correlations between cosmic voids and CMB temperature maps.