arXiv · 2503.13783
UNIONS: The Ultraviolet Near-Infrared Optical Northern Survey
Abstract
The Ultraviolet Near-Infrared Optical Northern Survey (UNIONS) is a "collaboration of collaborations" that is using the Canada-France-Hawai'i Telescope, the Pan-STARRS telescopes, and the Subaru Observatory to obtain $ugriz$ images of a core survey region of 6250 deg$^2$ of the northern sky. The $10\sigma$ point source depth of the data, as measured within a 2-arcsecond diameter aperture, are $[u,g,r,i,z] = [23.7, 24.5, 24.2, 23.8, 23.3]$\ in AB magnitudes. UNIONS is addressing some of the most fundamental questions in astronomy, including the properties of dark matter, the growth of structure in the Universe from the very smallest galaxies to large-scale structure, and the assembly of the Milky Way. It is set to become the major ground-based legacy survey for the northern hemisphere for the next decade and provides an essential northern complement to the static-sky science of the Vera C. Rubin Observatory's Legacy Survey of Space and Time. UNIONS supports the core science mission of the {\it Euclid} space mission by providing the data necessary in the northern hemisphere for the calibration of the wavelength dependence of the {\it Euclid} point-spread function and derivation of photometric redshifts in the North Galactic Cap. This region contains the highest quality sky for {\it Euclid}, with low backgrounds from the zodiacal light, stellar density, extinction, and emission from Galactic cirrus. Here, we describe the UNIONS survey components, science goals, data products, and the current status of the overall program.
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Stephen Gwyn, Alan W. McConnachie, Jean-Charles Cuillandre, Ken C. Chambers, Eugene A. Magnier, Michael J. Hudson, Masamune Oguri, Hisanori Furusawa, Hendrik Hildebrandt, Raymond Carlberg, Sara L. Ellison, Junko Furusawa, Raphaël Gavazzi, Rodrigo Ibata, Yannick Mellier, Ken Osato, H. Aussel, Lucie Baumont, Manuel Bayer, Olivier Boulade, Patrick Côté, David Chemaly, Cail Daley, Pierre-Alain Duc, A. Ellien, Sébastien Fabbro, Leonardo Ferreira, Itsna K. Fitriana, Emeric Le Floc'h, Hammer, Francois, Yoshinobu Fudamoto, Hua Gao, L. W. K. Goh, Tomotsugu Goto, Sacha Guerrini, Axel Guinot, Vincent Hénault-Brunet, Yuichi Harikane, Kohei Hayashi, Nick Heesters, Kohei Ichikawa, Martin Kilbinger, P. B. Kuzma, Qinxun Li, Tobías I. Liaudat, Chien-Cheng Lin, Oliver Müller, Nicolas F. Martin, Yoshiki Matsuoka, Gustavo E. Medina, Hironao Miyatake, Satoshi Miyazaki, Charlie T. Mpetha, Tohru Nagao, Julio F. Navarro, Masafumi Niwano, Itsuki Ogami, Nobuhiro Okabe, Masafusa Onoue, Gregory S. H. Paek, Laura C. Parker, David R. Patton, Fabian Hervas Peters, Simon Prunet, Rubén Sánchez-Janssen, M. Schultheis, Federico Sestito, Simon E. T. Smith, J. -L. Starck, Else Starkenburg, Connor Stone, Christopher Storfer, Yoshihisa Suzuki, Erben, T., Salvatore Taibi, G. F. Thomas, Zhang TianFang, Yoshiki Toba, Hisakazu Uchiyama, David Valls-Gabaud, Kim A. Venn, Ludovic Van Waerbeke, Richard J. Wainscoat, Scott Wilkinson, Anna Wittje, Taketo Yoshida, Yuxing Zhong. 2025-03-18. UNIONS: The Ultraviolet Near-Infrared Optical Northern Survey. https://arxiv.org/abs/2503.13783
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