Description

The Dark Energy Survey (DES) is a 5000 square degree survey of the Southern sky in grizY aimed at understanding the accelerating expansion of the Universe and the nature of dark energy. DES uses four complementary measurements to probe the evolution of the Universe: weak gravitational lensing, galaxy cluster counts, the large-scale clustering of galaxies (including baryon acoustic oscillations), and the distances to type Ia supernovae. DES uses the Dark Energy Camera (DECam), a 570 Megapixel CCD imaging camera with a 3 square degree field of view installed at the prime focus of on the Blanco 4m telescope at the Cerro Tololo Interamerican Observatory in northern Chile. DES observed for a period of six years (2013-2019), and has collected information from roughly 550 million distant galaxies and 150 million Milky Way stars. DES has also performed a 27 square degree time domain survey aimed at discovering thousands of supernova and other transients. The DES webpage contains a full description of the survey.

DES survey footprint from DES Collaboration (2021).

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Goals

The primary goal of the Dark Energy Survey is to measure the cosmic acceleration of the Universe with high precision. It does this with four complementary cosmological probes:
  • Supernovae. DES observes a 27 square degree area, distributed over several fields, with a weekly cadence aimed at discovering thousands of supernovae for use for cosmology.
  • Weak gravitational lensing. DES measures the total matter content and structure of the Universe via the weak gravitational lensing of distant galaxies.
  • Galaxy clusters. DES detects tens of thousands of galaxy clusters, the most massive gravitationally bound systems in the Universe.
  • Galaxy clustering. DES measures the spatial distribuiton of galaxies which is a sensitive probe of large-scale structure and the primordial distribution of matter.
The DES data enable many other exciting scientific studies, which can be explored through the DES public data releases.

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Data Releases

DES DR2

Documentation for DES DR2 can be found in DES Collaboration (2021).

DES DR2 Summary
Area covered ~5000 deg2
Bands grizY
Median catalog depth for 1.95 arcsec diameter aperture at S/N~10 in grizY 24.7, 24.4, 23.8, 23.1, 21.7 mag
Median PSF FWHM in grizY 1.11, 0.95, 0.88, 0.83, 0.90 arcsec
Median astrometric internal precision ~27 mas
Number of co-added image tiles / exposures 10,169 / 96,263
Number of objects / galaxies / stellar sources 691,483,608 / 543 million / 145 million
DES DR2 Tables
Table Name Description
main Main photometry; summary table
magnitude Magnitudes
flux Fluxes
coverage Coverage table; fraction of the Healpix 4096 (Nest) pixel covered by a certain band (values between 0 and 1)
des_dr2.x1p5__main__gaia_edr3__gaia_source Crossmatch of DES DR2 main table with Gaia EDR3 gaia_source table; 1.5 arcsec matching radius, single-nearest match only
des_dr2.x1p5__main__nsc_dr2__object Crossmatch of DES DR2 main table with NSC DR2 object table; 1.5 arcsec matching radius, single-nearest match only
des_dr2.x1p5__main__allwise__source Crossmatch of DES DR2 main table with AllWISE source table; 1.5 arcsec matching radius, single-nearest match only
des_dr2.x1p5__main__unwise_dr1__object Crossmatch of DES DR2 main table with unWISE DR1 object table; 1.5 arcsec matching radius, single-nearest match only
des_dr2.x1p5__main__sdss_dr16__specobj Crossmatch of DES DR2 main table with SDSS DR16 specobj table; 1.5 arcsec matching radius, single-nearest match only

DES DR1

Documentation on DES DR1 can be found in DES Collaboration (2018).

DES DR1 Summary
Area covered ~5000 deg2
Bands grizY
Median catalog depth for 1.95 arcsec diameter aperture at S/N~10 in grizY 24.45, 24.3, 23.5, 22.90, 21.70 mag
Median PSF FWHM in grizY 1.12, 0.96, 0.88, 0.84, 0.90 arcsec
Median astrometric internal precision ~30 mas
Number of co-added image tiles 10,338
Number of objects / galaxies / stellar sources 399,263,026 / 310 million / 80 million
DES DR1 Tables
Table Name Description
main Main object summary table
complement Secondary metadata
exposure Exposure information
hpix HEALPIX tile table
neighbors Objects within 30 arcsec
tile_info Tile information table
galex_des GALEX crossmatch
vhs_des VISTA Hemisphere Survey crossmatch
wise_des WISE crossmatch
band_g Single-band SExtractor table
band_i Single-band SExtractor table
band_r Single-band SExtractor table
band_y Single-band SExtractor table
band_z Single-band SExtractor table
vac_sextractor SExtractor summary table

To view the schema of any of these tables, use the Query Tool.


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Data Reduction

The DES data are processed through the DES Data Management (DESDM) pipeline, which includes image detrending and photometry (Morganson et al. 2018). The photometry is performed with modified versions of the Astromatic software suite, in particular the SExtractor and PSFEx packages. Users of these packages will find many of the column names in the DES tables to be familiar.

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