Dark Energy Survey

Dark Energy Survey. It is a major international, collaborative effort to map hundreds of millions of galaxies and detect thousands of supernovae to probe the nature of cosmic acceleration. The project was designed to constrain the properties of dark energy using four complementary observational methods. Data collection took place between 2013 and 2019 using a specially built, state-of-the-art camera on a large telescope in the Chilean Andes.

Overview

The project represents one of the most ambitious ground-based sky surveys ever undertaken in the field of cosmology. It was conceived to address fundamental questions raised by the landmark discoveries of the late 20th century, notably the accelerated expansion of the universe found by teams like the Supernova Cosmology Project and the High-Z Supernova Search Team. Primary operations were centered at the Cerro Tololo Inter-American Observatory, part of the U.S. National Science Foundation's NOIRLab. The collaboration involves over 400 scientists from institutions across the globe, including the lead laboratories Fermilab and the National Center for Supercomputing Applications.

Scientific goals and design

The primary scientific objective is to understand the nature of dark energy, the mysterious component causing the universe's expansion to accelerate. To achieve this, it employs four independent cosmological probes: measuring the large-scale structure of the universe through galaxy clustering and weak gravitational lensing, cataloging the abundance of massive galaxy clusters, and using Type Ia supernovae as standard candles. This multi-probe approach, championed by theorists like Joshua Frieman, helps to break degeneracies between cosmological parameters and test for potential deviations from the standard Lambda-CDM model. The survey area covers 5000 square degrees of the southern sky, avoiding the crowded plane of the Milky Way.

Instrumentation and observations

Observations were conducted using the 570-megapixel Dark Energy Camera, one of the most powerful digital imaging devices ever built. DECam was installed on the 4-meter Victor M. Blanco Telescope at Cerro Tololo. The camera's large field of view, about 3 square degrees, allowed it to capture vast swaths of sky in single exposures. It utilizes a set of five filters (g, r, i, z, Y) spanning optical to near-infrared wavelengths, which are critical for estimating precise photometric redshifts for distant galaxies. The survey obtained deep, multi-epoch imaging over 758 nights across six years, with data processed through sophisticated pipelines at the National Center for Supercomputing Applications and Fermilab.

Key findings and results

The collaboration has produced a wealth of cosmological constraints and astrophysical discoveries. Key results include some of the most precise measurements of the universe's matter density and the amplitude of matter clustering, consistent with but independent of those from the Planck (spacecraft) mission. It has produced the largest maps of cosmic mass distribution via weak lensing. The survey has also cataloged hundreds of millions of galaxies, discovered numerous distant solar system objects like the trans-Neptunian object 2015 TG387, and provided crucial data for studies of galactic structure. Its supernova program has yielded a large, cosmologically useful sample of Type Ia events.

Collaboration and data release

The collaboration is a consortium of research institutions from the United States, United Kingdom, Spain, Brazil, Germany, Switzerland, and Australia. Major partners include University College London, the Universidad Complutense de Madrid, and the Observatório Nacional in Brazil. Following a proprietary period for member scientists, the project makes its processed data publicly available through releases via the NOIRLab Astro Data Lab. These extensive public data sets, including the full first three years of data in the "DR1" release, serve as a lasting legacy resource for the entire astronomical community, enabling a wide range of research beyond the core dark energy science.

Category:Astronomical surveys Category:Cosmology Category:Dark energy