The Ultraviolet Near- Infrared Optical Northern Survey (UNIONS) is a collaboration between two the Hawai'ian observatories CFHT ( Canada-France-Hawaii Telescope on Mauna Kea) and Pan-STARRS (Panoramic Survey Telescope and Rapid Response System on Maui). Together they will observe the sky over 4,800 square degree in the northern hemisphere.
CFHT with the optical wide-field camera MegaCAM is mapping the sky in the r- and u-bands. This part of UNIONS is the Canada-France Imaging Survey (CFIS, to be read Sea-Fizz), observations have started in early February 2017 and are on-going as for mid-2020. The u-band data is part of the past LUAU survey, which will eventuall cover 10,000 square degrees. The data provided by UNIONS will be critical for the estimation of photometric redshifts, a requirement of paramount importance for the success of the Euclid mission.
It also allows for several science goals in various subfields of astrophysics to be reached directly. In particular, Weak Lensing studies can be performed based on CFIS images, a project in which several members of the CosmoStat team are heavily involved. Some of the main work the CosmoStat team is performing, or plans to perform, with CFIS data, is:
Development of the shear measurement pipeline ShapePipe (Samuel Farrens, Axel Guinot, Martin Kilbinger)
Comparison of different tracers of Dark Matter, including mass mapping and peak counts (Martin Kilbinger, Jean-Luc Starck et al.)
Exploration of modified gravity models (Valeria Pettorino)
Cross-correlation with SDSS and test of General Relativity (Axel Guinot, Martin Kilbinger)
Application of novel methods of PSF estimation developed in-house (Tobias Liaudat, Jean-Luc Starck et al.)