Dark Energy Camera Legacy Survey Announces Second Data Release

Two bright galaxies imaged by DECaLS: UGC 12589 (left) and UGC 9968 (right).

The Dark Energy Camera Legacy Survey (DECaLS) announced its second data release (DR2) on 15 January 2016. DECaLS (PIs: David Schlegel and Arjun Dey) is in the middle of mapping 6200 square degrees of the extragalactic sky in g, r and z using the Dark Energy Camera on the Blanco 4-m telescope at the Cerro Tololo Inter-American Observatory. The project is designed to investigate a broad range of astrophysical questions, ranging from studies of Milky Way structure and galaxy evolution to large-scale structure and cosmology. The survey goals and the first data release were described in an earlier issue of Currents.

DECaLS DR2 includes reduced images and source catalogs covering approximately 2100 square degrees of sky in g- and r-band and 5300 square degrees in z-band. Roughly 1800 square degrees has been imaged in all three bands. The area covered can be visualized using the project’s Imagine Sky Viewer built by Dr. Dustin Lang. An Image Gallery of Large Galaxies constructed by Dr. John Moustakas is also available.

DR2 includes not only all the data taken by DECaLS from August 2014 through June 2015, but also all public DECam g-, r-, and z-band data within the DECaLS footprint obtained by other projects. The latter include data (now public) from the Dark Energy Survey in the “Stripe 82” region.

Mapping the Sky. 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 begins in February 2016, and the Beijing-Arizona Sky Survey (BASS), which is 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.

Making it Public. All three surveys are being run as public projects, with no proprietary period for the raw data. Reduced images are available as soon as the pipeline processing at NOAO is complete, and official data releases are scheduled every 6 months. All of the data will be served by the NOAO Science Archive and the National Energy Research Scientific Computing Center at the Lawrence Berkeley National Laboratory. For further details, please see legacysurvey.org.