DECam Legacy Survey

DECam Legacy Survey
Felipe Menanteau and the Dark Energy Survey Collaboration · CC BY-SA 4.0 · source
Name	DECam Legacy Survey
Telescope	Víctor M. Blanco Telescope
Instruments	Dark Energy Camera
Start date	2013
End date	2019
Area	14,000
Wavelength	Optical

DECam Legacy Survey is a wide-field optical imaging program conducted with the Víctor M. Blanco Telescope's Dark Energy Camera at Cerro Tololo Inter-American Observatory to provide target catalogs and photometry for spectroscopic programs and cosmological analyses. The project produced multi-band imaging used by projects involving Sloan Digital Sky Survey follow-ups, Dark Energy Spectroscopic Instrument, and legacy archives associated with NOIRLab, Lawrence Berkeley National Laboratory, and National Optical-Infrared Astronomy Research Laboratory. The survey bridged datasets from predecessors and contemporaries such as Pan-STARRS, DES, LSST, CFHT Legacy Survey, and GALEX to support programs led by institutions including University of Arizona, Harvard University, University of Chicago, Yale University, and Stanford University.

Overview

The survey delivered deep g, r, z imaging designed to complement spectroscopic campaigns like Dark Energy Spectroscopic Instrument and imaging surveys like Wide-field Infrared Survey Explorer and Two Micron All-Sky Survey while interfacing with catalogs from Gaia, Hubble Space Telescope, Spitzer Space Telescope, Chandra X-Ray Observatory, and XMM-Newton. Leadership included scientists affiliated with Lawrence Berkeley National Laboratory, Fermilab, NOAO/NOIRLab, University of Michigan, and Instituto de Astrofísica de Canarias collaborating with teams connected to SLAC National Accelerator Laboratory, Kavli Institute for Cosmological Physics, Max Planck Institute for Astronomy, Max Planck Institute for Astrophysics, and Institute for Astronomy, University of Hawaii.

Instrumentation and Observations

Imaging was obtained with the Dark Energy Camera, a wide-field imager built by consortia including FNAL, KIPAC, CEA Saclay, University College London, and Brookhaven National Laboratory, mounted on the Víctor M. Blanco Telescope at Cerro Tololo Inter-American Observatory operated by NOIRLab and managed under programs involving NSF and DOE. Observations were scheduled to coordinate with seeing and moon constraints used by contemporaneous campaigns such as Dark Energy Survey and coordinated with follow-up from facilities like Gemini Observatory, Keck Observatory, Magellan Telescopes, and Very Large Telescope. The instrument utilized CCDs produced by teams including LBNL and electronics work by SLAC National Accelerator Laboratory collaborators; survey operations engaged staff from Carnegie Institution for Science, University of Washington, University of Illinois Urbana-Champaign, and University of California, Berkeley.

Data Processing and Products

Raw data were processed through pipelines developed with contributions from NOIRLab, Lawrence Berkeley National Laboratory, Fermilab, and software groups connected to Astropy Project and IPAC. The data products included calibrated images, stacked coadds, photometric catalogs, astrometric solutions tied to Gaia reference frames, and value-added catalogs for target selection for DESI. Releases were archived at repositories managed by NOIRLab, NCSA, NERSC, and distributed through portals used by researchers at Harvard-Smithsonian Center for Astrophysics, Princeton University, Columbia University, University of Oxford, and Cambridge University. Processing leveraged algorithms and tools used by projects like SExtractor, SWarp, SCAMP, and pipelines inspired by SDSS processing strategies endorsed by groups at Apache Point Observatory and University of Tokyo collaborators.

Scientific Goals and Key Results

Primary goals included supporting large-scale structure measurements, photometric redshift catalogs, target selection for Dark Energy Spectroscopic Instrument, studies of galaxy evolution, and searches for faint dwarf galaxies and transients in coordination with observatories like Pan-STARRS, Zwicky Transient Facility, LSST Science Collaboration, and Arecibo Observatory legacy data. Science outcomes involved improved photometric redshift performance used in analyses by teams from Carnegie Mellon University, University of Pennsylvania, Rutgers University, and University of Colorado Boulder; discoveries of faint Milky Way satellites relevant to work by Max Planck Institute for Astronomy and Kavli Institute; mapping of large-scale structure informing studies by Institute for Advanced Study and CERN collaborators; and cross-correlation studies with Planck and WMAP microwave background results. Survey-derived catalogs were incorporated into investigations by researchers at Yale University, Johns Hopkins University, University of Edinburgh, University of Toronto, and University of British Columbia.

Survey Footprint and Depth

Observations covered roughly 14,000 square degrees across the northern and southern Galactic caps overlapping footprint regions of SDSS and Pan-STARRS, with depths comparable to or deeper than legacy surveys in g, r, z bands enabling target selection to magnitude limits used by DESI and complementary to Euclid field planning. The footprint was designed to intersect spectroscopic programs affiliated with 2dFGRS fields, legacy areas from GAMA, and to maximize overlap with space missions like GALEX and WISE while avoiding regions dominated by extinctions mapped by studies from COBE teams and cross-checked with IRAS maps.

Collaboration, Funding, and Timeline

The project was executed by a collaboration of institutions including Fermilab, Lawrence Berkeley National Laboratory, NOIRLab, University of Arizona, University of Chicago, Carnegie Institution for Science, Stanford University, Harvard University, Princeton University, and international partners like University of Edinburgh, Max Planck Society, CEA Saclay, and DESY. Funding sources included agencies such as National Science Foundation, Department of Energy, institutional contributions from University of Michigan and University of Washington, and international support from organizations like UKRI affiliates and European consortia connected to European Southern Observatory and CNRS. Survey planning began in the early 2010s, observations ran primarily between 2013 and 2019, and data releases were staged to support commissioning of spectroscopic facilities such as Dark Energy Spectroscopic Instrument and preparatory science for Vera C. Rubin Observatory operations.

Category:Sky surveys