Canada-France Imaging Survey (CFIS UNIONS)


The Canada-France Imaging Survey (CFIS*) from the Ultraviolet Near Infrared Optical Northern Survey (UNIONS) is a legacy survey that will address some of the most fundamental questions in astronomy: the properties of dark matter and dark energy, the growth of structure in the Universe from Galactic to cluster scales, and the assembly of the Milky Way. These ambitious goals are achievable only with homogeneous, multiwavelength data covering large areas of the sky. CFIS exploits the unparalleled u-band sensitivity, excellent r-band image quality (IQ) of CFHT through two related survey components, enabling discoveries about structure formation from the Milky Way to high redshifts. The legacy value of CFIS will be its contribution to existing and future deep, wide-field northern surveys, leveraging the premier capabilities of CFHT. CFIS represents a critical component of the data needed for photometric redshifts in the Euclid space mission, and thus enables a Stage IV measurement of dark energy properties. It is also designed to complement existing northern sky imaging and the SDSS and DESI spectroscopic surveys. This synergy will enable countless new discoveries.

* Pronounced "Sea-Fizz"

CFIS is a CFHT Large Program that has been allocated 271 nights over six semesters (17A to 19B, from Feb. 1st 2017, to Jan. 31st 2020) but has since been extended (+75 nights) to July 31st 2022 due to adverse weather conditions. It has two survey components:

  • CFIS-r (Wide + Image Quality + Deep) will image ~5000 square degrees over 154 nights in the r-band. Covering the sky above a declination of 30 degrees, and outside the galactic plane, it will produce a panoramic survey with exquisite image quality (~0.6 arcsecond) to a depth of 24.1 (point source, SNR=10, 2 arcseconds diameter aperture).

  • CFIS-u (continuation of the Legacy for the U-band All-sky Universe - Luau - program) will survey ~10000 square degrees over 117 nights, covering the region above a declination of 0 degrees, and outside the galactic plane, to a u-band depth of 23.6 (point source, SNR=10, 2 arcseconds diameter aperture).

Proprietary time & Public release
The CFIS is a legacy survey for the Canadian and French communities. All data are proprietary within the Canadian and French communities until Aug. 1st, 2023 when the individual frames will become available to the worldwide community. Advanced curated CFIS data products will be made available to the world as part of UNIONS public data releases.

The CFIS Collaboration
The CFIS Collaboration is a joint Canadian and French community of 100+ scientists, mainly composed of the 2016 CFIS proposal co-Is, whose principal goals are to do great science and to ensure the production of a legacy quality dataset for the public release.

The Canada-France-Hawaii Telescope
The Canada-France-Hawaii Telescope (CFHT) is a non-profit organization that operates a world class 3.6 meter telescope atop Maunakea, a dormant Hawaiian volcano rising 4,200 meters (14,000 feet) above the Pacific Ocean. The observatory headquarters are located nearby in Waimea (Kamuela, Big Island, Hawaii), where CFHT has been part of the community since 1977. The CFHT team of some 40 people includes engineers, technicians, astronomers, and administrators. The role of CFHT is to operate, maintain and upgrade all the observatory systems, to make sure that the telescope remains scientifically competitive, and to provide first rate instrumentation to its users community : CFHT is currently open to astronomers from Canada, France and Hawaii, as well as the European Union through Opticon and Taiwan through collaboration agreements. The CFHT is operated by the National Research Council of Canada, the Centre National de la recherche Scientifique of France and the University of Hawaii

MegaCam is the wide-field optical imaging facility at CFHT. MegaCam (built by CEA Saclay, France), consists of 40 2048 x 4612 pixel e2v CCDs (a total of 380 megapixels), covering a full 1 x 1 square degree field-of-view with a resolution of 0.187 arcsecond per pixel which properly samples the 0.6 arcsecond median seeing offered by the CFHT at Mauna Kea, with the newly vented dome. The prime focus upper end, MegaPrime, includes an image stabilization unit and a guide/autofocus unit. More than a decade after its first light, MegaCam remains the workhorse instrument at CFHT and it still uses most of the telescope dark time to conduct Principal Investigators led scientific programs as well as large programs such as the CFIS.

Maunakea ("White Mountain" in Hawaiian due to its snow-capped summit) is a dormant volcano located on the Big Island (Hawai'i) in the state of Hawaii. It is the best ground-based astronomical observing site in the northern hemisphere. The observatories on Maunakea benefit from the high altitude (14,000 feet, or 4,200 meters), which allows for a clearer, dryer atmosphere, a darker sky, more clear nights per year and, most importantly, sharper images thanks to low atmospheric turbulence at the top of the mountain.