2025A - 2026B CFHT Large Programs

As proposed in its 10-year plan, CFHT offered up to 400 nights for Large Programs to be executed over a maximum of 1.5 years for MegaCam, and a maximum of 2 years for ESPaDOnS and SPIRou, in 2025 and 2026.

NRC (Canada) and CNRS (France) offered up to 70% of their agency time for this round of Large Programs.

Out of the 400 nights offered, 330 nights were awarded to the following Large Programs:

UNIONS+: Securing the Imaging Legacy of CFHT

PI: Dr. Alan McConnachie, Jean-Charles Cuillandre, Stephen Gwyn

Instrument: MegaCam, 60 nights allocated, semesters 25B, 26A, and 26B.

Abstract -- The Ultraviolet Near Infrared Optical Northern Survey (UNIONS) is the definitive large area multi-band (u,g,r,i,z) ground-based wide-field survey in the northern hemisphere. It is also the vital data set necessary to enable the core science of the Euclid space mission, successfully launched last year and now undertaking its long anticipated survey of the sky that will provide a Stage IV cosmological measurement. More than 1 billion Euro has been invested in Euclid to deliver its 13,245 square degree survey: the northern part of this survey is entirely dependent upon UNIONS to provide the complementary ground based data. Seen in this light, it is crass but true that every additional 10% of sky coverage observed by UNIONS, as presented in this proposal, represents an additional 100 million Euro of scientific return. The goal of the current proposal is to extend the current CFHT coverage from Dec=30 down to Dec=15. When the original CFIS Large Program began, it was envisioned that the LSST would survey up to Dec=30 in support of Euclid. However in 2022 LSST decided to limit its surveys to Dec=15 over the north galactic cap. This motivates the current extension: this proposal is to image the missing stripe between Dec=15 and Dec=30 (1335 square degrees) in u and r. The north galactic cap covered by UNIONS contains the highest quality sky for Euclid (low on background from the zodiacal light, stellar density, extinction and emission from galactic cirrus), a primary driver for the space survey design. With this extended area, UNIONS will contribute a total of 43% of the Euclid ground-based coverage, the remaining 57% coming from LSST. Without the ground-based colours, the Euclid data have greatly diminished value. We are therefore requesting a total of 504 hours (split 50/50 between Canada and France), minus any time that is successfully observed in 25A as part of the current UNIONS allocation (90.5 hours in 24B/25A). UNIONS is a collaboration of three major facilities - Subaru, Pan-STARRS, and CFHT. Today, there are 240 members of UNIONS worldwide, not including the (literally) thousand scientists in Euclid which are dependent upon UNIONS data. In parallel with this proposal, the UNIONS collaboration is pursuing extensions to the g, i and z bands on these other Hawaii-based facilities. UNIONS is providing answers on its own to 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 cluster scales, and the assembly of the Milky Way. CFHT/MegaCam provides the unparalleled u-band sensitivity, excellent r-band performance and recovered image quality that are a foundational contribution to UNIONS. This proposal represents a significant growth in the importance of UNIONS to Euclid. By stepping up to this challenge, UNIONS and CFHT will secure their legacy in this transformational era of wide field astronomy.

Website: Canada-France Imaging Survey (CFIS UNIONS)

PLANETS: PLanets, Atmospheres, and Nativity of ExtraTerrestrial worldS

PI: Dr. Jean-François Donati

Instrument: SPIRou, 240 nights allocated, semesters 25A, 25B, 26A, and 26B.

Abstract -- Building up on the extensive results of the SLS and SPICE LPs with SPIRou, PLANETS will now focus on very-low-mass nearby M dwarfs to unveil and characterize their planetary systems, on low-mass pre-main sequence stars whose accretion processes, inner accretion discs and inner planetary systems will be investigated to improve our understanding of star / planet formation, and on a handful of exoplanet atmospheres to be repeatedly scrutinized in order to accurately quantify their physical properties. Mostly carried out with SPIRou, PLANETS will exploit in particular key synergies with complementary instruments such as ESPaDOnS, TESS, NIRPS, VLTI/GRAVITY, and JWST to boost science output and go beyond current conceptual limitations in our understanding of the physical processes under investigation. Altogether, PLANETS requires 305 CFHT nights (293 with SPIRou and 12 with ESPaDOnS) to reach its science goals. For this ambitious program, high monitoring rates of most targets over consecutive seasons is mandatory, an observing condition that only an LP like PLANETS can achieve in practice.

Website: The SPIRou Legacy Survey (SLS) & SPICE & PLANETS

The Pristine LP: mapping the metallicity of the Milky Way system

PI: Dr. Nicolas Martin

Instrument: MegaCam, 30 nights allocated, semesters 25B, 26A, and 26B.

Abstract -- We propose to build on our extensive expertise of CFHT, MegaCam, and its excellent, metallicity-sensitive Ca H&K filter to push the Pristine survey that studies the oldest stars in the Milky Way to a new level. We have developed extensive expertise in inferring accurate metallicities of stars observed through this filter, isolating the metal-poor (old) Milky Way (MW) stars from their much more numerous recent (metal-rich) stars, thereby allowing us to glimpse at the build up of the Galaxy and hunt for the first generations of stars. The proposed observations will significantly expand on this foundation to deconstruct the MW in its different environments (disk, halo, satellites) to enable a direct and thorough comparison with expectations from galaxy formation and evolution models. At the same time, any additionally uncovered extremely metal-poor stars ([Fe/H]<–3.0) with this LP program will contribute significantly to the hunt for the first generation of stars and can be seamlessly added to our already secured follow-up within the context of the WEAVE multi-object spectroscopic survey (MoU already signed). Together, this program will both unveil the formation of the MW within its first 2 Gyr and explore the properties of the first generations of stars. To fulfill these ambitious goals, our program is built around three complementary tiers: Tier 1: Provide a full, Gaia-depth coverage of the footprint of the WEAVE Galactic Archaeology halo survey to maximize the construction of the largest sample of the most metal-poor stars ([Fe/H]<–3.0) and their secured follow-up with detailed spectroscopy. Tier 2: Probe in detail the halo/disk interface in the anticenter direction with a contiguous survey to explore the puzzling presence of a significant fraction of disk-like stars among even the lowest metallicity samples. Does it mean that the MW disk was in place earlier than previously thought? That these stars formed in the disk from pockets of gas that remained pristine despite ongoing star formation? That they were brought here through accretions? Tier 3: Provide a deep survey of the bright (metal-poor) MW dwarf galaxies and their surroundings to fully determine their metallicity content and their full extent. These observations are essential to place dwarf galaxies the context of ΛCDM galaxy formation as they are heralded as powerful probes of the cosmological model. To enhance the legacy value of the Large Program, we will commit to releasing dedicated, regular data releases of reduced data and metallicity catalogues. CFHT is uniquely suited to this program with its access to the northern sky as well as the efficient MegaCam/CaHK filter. Only a Large Program can ensure we reach the ambitious science goals proposed above given the depth and/or coverage by the three tiers of the program.

Website: The Pristine survey