Free Astronomy Magazine May-June 2023

19 MAY-JUNE 2023 ASTRO PUBLISHING This effort culminated in the largest two-dimen- sional map of the sky ever created. With col- lective observations by the Mosaic-3 camera on the Nicholas U. Mayall 4- meter Telescope and the 90Prime camera on the University of Arizona Bok 2.3-meter Telescope, both located at KPNO, as well as the DOE-built Dark Energy Camera (DECam) on the Víctor M. Blanco 4-meter Tele- scope at CTIO in Chile. One of the main pur- poses of this map is to identify roughly 40 mil- lion target galaxies for the five-year DESI Spec- troscopic Survey, which is aimed at understanding dark energy by pre- cisely mapping the expansion history of the Universe over the last 12 bil- lion years. The DESI project has selected its tar- gets and the spectroscopic survey is currently underway. However, the team is looking to create the most comprehensive map of the sky that they can, so more images and im- proved processing have been added to the Legacy Surveys to include data that were previously missing. Most notably, the tenth data re- lease focuses on integrating new imaging from DECam of the south- ern extragalactic sky, especially in areas away from the Milky Way’s disk, which are ideal for looking far into the cosmos. With the addition of southern sky images in the new data release, the Legacy Surveys have been expanded to over 20,000 square degrees, nearly half the sky. In addition, the new release includes images of the sky taken in an additional color fil- ter, able to sample infrared light just redder than what the human eye many; the DECam Local Volume Exploration Sur- vey; and the final (sixth) year of the Dark Energy Survey. The team also scoured the NSF NOIR- Lab data archive to use any public data of the sky that already existed or was being collected by other researchers. It’s not only scientists who benefit from the grow- ing archive of astro- nomical data coming out of the Legacy Sur- veys. The publicly avail- able data make it possible for astronomy enthusiasts and curious individuals to digitally peruse the Universe around us. “Anyone can use the sur- vey data to explore the sky and make discoveries,” said Arjun Dey, an astronomer with NSF’s NOIRLab. “In my opinion it is this ease of ac- cess which has made this survey so impactful. We hope that in a few years the Legacy Surveys will have the most complete map of the en- tire sky, and provide a treasure trove for scientists well into the future.” NOIRLab will host these data prod- ucts in the Astro Data Archive, from the original images taken at the telescopes to the catalogs that re- port the positions and other prop- erties of stars and galaxies. Astro Data Lab, which is part of the Com- munity Science and Data Center (CSDC) at NSF’s NOIRLab, also serves the catalogs as databases, which as- tronomers can easily analyze using the Astro Data Lab tools and serv- ices, and cross-match them with other datasets, giving more oppor- tunities for discovery. In addition, Astro Data Lab provides astronomers with example scientific applications and tutorials to assist with their research. T he Nicholas U. Mayall 4-meter Telescope, named for the former Director of the Kitt Peak National Observatory, was the second- largest telescope by aperture at the time of its first light in 1973. The telescope currently hosts the Dark Energy Spectroscopic Instru- ment (DESI), the most powerful multi-object survey spectrograph in the world. [José Francisco Salgado] ! can see. The additions to the map’s footprint and wavelength coverage will in turn make the data useful to a wider demographic of scientists. “The addition of near-infrared wave- length data to the Legacy Survey will allow us to better calculate the redshifts of distant galaxies, or the amount of time it took light from those galaxies to reach Earth,” said Alfredo Zenteno, an astronomer with NSF’s NOIRLab and principal in- vestigator of DECam eROSITA Survey (DeROSITAS). “This is essential for surveys at radio and X-ray wavelengths that need the complete ‘optical’ view to iden- tify the origin of the emission, like clusters of galaxies and active su- permassive black holes,” said Mara Salvato, a researcher at the Max Planck Institute for Extraterrestrial Physics (MPE) and spokesperson for eROSITA. The bulk of these additional DECam observations are from the DeROSI- TAS team, which includes scientists from NSF’s NOIRLab, the University of La Serena, MPE and Ludwig Max- imilians University Munich in Ger-