Description

The Dark Energy Survey (DES) is a 5000 square degree grizY survey of the Southern sky aimed at understanding the accelerating expansion rate of the Universe. DES is using four complementary methods to do this: weak gravitational lensing, galaxy cluster counts, baryon acoustic oscillations, and Type Ia supernovae. DES uses the 3 square degree Dark Energy Camera (DECam), a 570 Megapixel CCD imaging camera installed at the prime focus of on the Blanco 4m telescope at the Cerro Tololo Interamerican Observatory in northern Chile. The survey is being performed over a period of five years (2013-2018), and is recording information from roughly 300 million distant galaxies and 100 million Milky Way stars. DES is also pursuing a time domain survey over a 30 square degree area aimed at discovery of thousands of supernova and other transients. The DES Survey page contains a full description of the survey.

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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 is using four probes to do so:
  • Supernovae. DES observes a 30 square degree area, distributed over several fields, with a cadence aimed at discovering thousands of supernovae for use for cosmology.
  • Weak gravitational lensing. The DES Collaboration is using the galaxies discovered by DES to make three dimensional mass maps through weak lensing, for analysis of the growth of structure.
  • Galaxy clusters. Galaxy clusters are another probe of the growth of structure. Cosmological results from weak lensing and cluster analysis from the Year 1 data are available here.
  • Baryon Acoustic Oscillations. The galaxies discovered by DES provide a sample to measure the evolution of the length imprinted on the matter distribution at the time of last scattering after the Big Bang.
The DES data will serve many other science cases, which are enabled by the DR1 release.

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Data Release

DES DR2 data products will be available at Astro Data Lab from Jan 15, 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 / single-epoch images 10,169 / 76,217
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_dr2__gaia_source Crossmatch of DES DR2 main table with Gaia DR2 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 Summary
Area covered 5000 deg2
Bands grizY
Depth (10σ, grizY) 24.45, 24.3, 23.5, 22.90, 21.70 mag
Seeing (grizY) ~1 arcsec
Number of Tiles 10338
Number of objects 399,263,026
DES DR1 Tables
Table Name Description
complement Secondary metadata
exposure Exposure information
hpix HEALPIX tile table
main Main object summary 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

As described on the DES web page, the DES data are processed through the DES Data Management (DESDM) pipeline, which includes image detrending and photometry. 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 DR1 tables to be familiar.

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