Thursday, November 24, 2016

Third Data Release for DECam Legacy Survey

DECaLS DR3 data (top) reach significantly deeper than SDSS images (bottom). In addition to foreground stars, nearby galaxy UGC4640 and many distant galaxies are visible within this 7.5’x5’ field-of-view.

The DECam Legacy Survey (DECaLS) has announced its third data release. An NOAO Survey Program led by co-PIs David Schlegel (LBNL) and Arjun Dey (NOAO), DECaLS uses the Dark Energy Camera (DECam) on the CTIO Blanco 4m telescope to image nearly square degrees of the extragalactic sky in three bands (g, r and z). Earlier data releases were made in June 2015 (DR1) and February 2016 (DR2). The current status of the survey is shown here

The third data release (DR3), which covers [4300, 4600, 8100] square degrees in [g, r, z] bands respectively, includes catalogs and images obtained between August 2014 and March 2016. DR3 also incorporates public data within the DECaLS footprint from other NOAO observing programs and photometry from NASA’s Wide-Field Infrared Surveyor’s maps of the sky. 

The final DECaLS sky coverage will extend in declination from approximately -18 to +30 degrees, and cover Galactic latitudes |b| > 18 degrees. The survey also overlaps the SDSS/BOSS extragalactic footprint. DECaLS will allow astronomers to probe the structure of the Milky Way, the nature of dark energy, and many other topics in astrophysics. All data are immediately non-proprietary and the project schedules two data releases per year.

The DR3 release includes raw data, individual calibrated DECam exposures, image coadds in 0.25x0.25 square degree “bricks”, source catalogs containing approximately 478 million unique sources, and an interactive sky viewer interface. An Image Gallery of Large Galaxies constructed by Dr. John Moustakas is also available. For further information regarding DR3, please see the survey website

DECaLS is one of three surveys that will jointly image 14,000 square degrees—nearly one-third of the sky—to provide targets for the Dark Energy Spectroscopic Instrument cosmology project. The other two projects are the Mayall z-band Legacy Survey (MzLS), which began in February 2016, and the Beijing-Arizona Sky Survey (BASS), currently underway at the Bok Telescope on Kitt Peak. MzLS and BASS will provide g- ,r-, and z- band imaging at declinations north of +34 degrees.

DECaLS DR3 data products are available through the NOAO Science Archive and ftp server. In addition, the NOAO Data Lab has developed a database to query all DR3 catalogs, which is available by contacting the Data Lab directly (

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