Abstract
Abstract We present the second public data release of the Dark Energy Survey, DES DR2, based on optical/near-infrared imaging by the Dark Energy Camera mounted on the 4 m Blanco telescope at Cerro Tololo Inter-American Observatory in Chile. DES DR2 consists of reduced single-epoch and coadded images, a source catalog derived from coadded images, and associated data products assembled from 6 yr of DES science operations. This release includes data from the DES wide-area survey covering ∼5000 deg2 of the southern Galactic cap in five broad photometric bands, grizY. DES DR2 has a median delivered point-spread function FWHM of g = 1.11″, r = 0.95″, i = 0.88″, z = 0.83″, and Y = 0.″90, photometric uniformity with a standard deviation of < 3 mmag with respect to Gaia DR2 G band, a photometric accuracy of ∼11 mmag, and a median internal astrometric precision of ∼27 mas. The median coadded catalog depth for a 1.″95 diameter aperture at signal-to-noise ratio = 10 is g = 24.7, r = 24.4, i = 23.8, z = 23.1, and Y = 21.7 mag. DES DR2 includes ∼691 million distinct astronomical objects detected in 10,169 coadded image tiles of size 0.534 deg2 produced from 76,217 single-epoch images. After a basic quality selection, benchmark galaxy and stellar samples contain 543 million and 145 million objects, respectively. These data are accessible through several interfaces, including interactive image visualization tools, web-based query clients, image cutout servers, and Jupyter notebooks. DES DR2 constitutes the largest photometric data set to date at the achieved depth and photometric precision.
Highlights
Advances in telescope construction, sensor technology, and data processing have allowed us to map the sky with increasing speed and precision, enabling discovery through statistical analysis of astronomical source populations, as well as the detection of rare and/or unexpected objects (Tyson 2010)
Together with access to the software used to generate these products and the configuration described in Morganson et al (2018), we provide the main ingredients to reprocess the data in a manner similar to that done by Dark Energy Survey (DES)
DES has provided a deep view of the south Galactic cap with precise grizY photometry that will reach ∼24th magnitude in the i band over ∼5000 deg2
Summary
Sensor technology, and data processing have allowed us to map the sky with increasing speed and precision, enabling discovery through statistical analysis of astronomical source populations, as well as the detection of rare and/or unexpected objects (Tyson 2010). The instrumental and observational strategies of DES are designed to improve our understanding of cosmic acceleration and the nature of dark energy using four complementary methods: weak gravitational lensing, galaxy cluster counts, the large-scale clustering of galaxies (including baryon acoustic oscillations), and the distances to Type Ia supernovae (SNe; DES Collaboration 2005). At NCSA, the DES Data Management system (DESDM; Sevilla et al 2011; Desai et al 2012; Mohr et al 2012; Morganson et al 2018) generates a variety of scientific products, including single-epoch and co-added images with associated source catalogs of suitable quality to perform precise cosmological measurements (e.g., DES Collaboration 2017). Raw DES exposures become publicly available 1 yr after acquisition from the National Optical Astronomy Observatory (NOAO) Science Archive, and DES is scheduled to provide two major public releases of processed data. All magnitudes quoted in the text are in the AB system (Oke 1974)
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