Large Programs [2013 - 2016]

These large programs are the current ones executed by CFHT.

the Outer Solar System Origins Survey (OSSOS)

PI: Gladman

Instrument: MegaPrime, 560 hours, spread over all 8 semesters

Web site


Progress in studies of planet formation and migration are exhausting the available Kuiper Belt data set. There are simply not enough objects detected in well-calibrated samples to judge the veracity of proposed models of planet formation, initial radial planetesimal distribution, and migration distances or time scales. We propose a 4-year program to find and track more than 1000 trans-neptunian (and closer) objects in our outer Solar System using Megaprime. Due to the proven flexibility provided by CFHT QSO’s implementation of Megaprime’s capabilities, CFHT is the only wide field telescope that is realistically able to provide the data to build such a sample. Because precise orbit determination is vital to the science goals which choose between theoretical models, tracking large sky patches (21 square degrees each) will allow OSSOS to provide an object sample along with a calibrated Survey Simulator that will make this survey vastly more powerful at model descrimination than existing data sets, allowing ‘precision Solar System science’. By focussing on the sky’s resonant sweet spots, we will maximize the science impact of our detected sample. OSSOS will allow the CFHT community to lead the world in this field during this decade.

CFHT-Luau: The CFHT Legacy for the u-band all-sky universe

PI: McConnachie and Ibata

Instrument: MegaPrime, 350 hours, spread over semesters 15A to 16B.


We propose CFHT-Luau, an ambitious u band survey of the northern sky. In this first phase, we were allocated 350 hours to survey 4000 square degrees that lies within the SDSS footprint. When combined with existing SDSS griz data, we will make the most precise reconstruction of the metallicity structure of the Galaxy by mapping the distances and metallicities of >10 million main sequence stars. We will also identify every blue horizontal branch star to half the virial radius of the Galaxy, and produce the definitive catalog of disk and halo white dwarfs within 1kpc. The potential legacy value of these data both in and beyond Galactic astronomy is immense, and Luau can be expected to make critical contributions in the determination of photometric redshifts, galaxy evolution, and many other fields. The opportunity for leveraging these data by the community is huge. Luau will allow an unprecedented study of the stellar populations and structure of the outer Galaxy, and takes advantage of the capabilities of CFHT/MegaCam to produce the definitive survey of the u-band Universe. It will give CFHT a powerful legacy that lasts beyond the next generation of wide field surveys.

Mass Assembly of early-type GaLAxies with their fine Structures (MATLAS)

PI: Duc

Instrument: MegaPrime. 300 hours, spread over 5 semesters


MATLAS investigates the mass assembly of Early-Type Galaxies (ETGs) and the build-up of their scaling relations, with extremely deep optical images. The stellar populations in the outermost regions of ETGs, the fine structures (tidal tails, stellar stream, and shells) around them, and the Globular Cluster (GCs) populations, preserve a record of past merger events and more generally of the evolution and transformation of galaxies. The project capitalizes on several timely developments 1) The unique capabilities of MegaCam. Dedicated imaging procedures and a new pipeline now allow the detection of surface brightness structures, as faint as 29 mag/arcsec2 in the g band. We will thus apply a technique of galaxy archeology, that was first tested on local spirals, to lenticulars/ellipticals which are expected to exhibit many more relics of their mass assembly. The feasibility of the method was validated with pilot surveys 2) An already available stunning ancillary dataset provided by the ATLAS3D project giving complementary information on their dynamics, gas and stellar content. 3) State of the art numerical simulations developed by our team. They predict various types of fine-structures and stellar halos depending on the mechanism driving the mass assembly: major or minor, wet or dry mergers; secular evolution. The database collected as part of this Large Programme and earlier observations, consisting of multi-color images for a volume limited sample of 260 nearby ETGs - the ATLAS3D sample - will have a tremendous legacy value. It will also allow detailed studies of individual well-known objects, rejuvenated with the unprecedented deep images, and to address broader science topics, such as the origin of the galaxy scaling relations, that require complete samples. Finally this LP has a strong appeal for public outreach.

Binarity and Magnetic Interactions in various classes of Stars (BinaMIcS)

PI: Alecian/Wade

Instrument: ESPaDOnS. 604 hours, spread over 8 semesters.


Magnetic fields are a crucial ingredient in a star’s evolution, influencing its formation, the structure of its atmosphere and interior, as well as controlling the interaction with its environment. For binary stars magnetism is even more significant, as magnetic fields in binary systems will be strongly affected by, and may also strongly affect, the transfer of energy, mass and angular momentum between the components in these important stellar systems. However, the interplay between stellar magnetic fields and binarity has yet to be investigated in any real detail, from either an observational or theoretical point-of-view. Nevertheless, the incidence and characteristics of magnetic fields are key parameters for understanding the physics of binaries. In higher-mass stars (above 1.5 Msun) the incidence of magnetic stars in binary systems provides a basic constraint on the detailed origin of the magnetic field, assumed to be fossil remnant, and whether such strong magnetic fields suppress binary formation. In low-mass stars, tidal interactions are expected to induce large-scale 3D shear and/or helical flows in stellar interiors that can significantly perturb the stellar dynamo. Similar flows may also influence the fossil magnetic fields of higher-mass stars. Magnetically driven winds/outflows in cool and hot close binary systems have long been suspected to be responsible for their orbital evolution, while magnetospheric interactions have been proposed to enhance stellar activity. However, the crucial observational constraints required to test these hypotheses are, at present, nearly nonexistent. The BinaMIcS project represents an innovative large program with ESPaDOnS to study the complex phenomenon of stellar magnetism under the influence of the unique physical processes and interactions occurring in close binary systems. Using cutting-edge observations, sophisticated theory and realistic simulations, we will observe and model the magnetic fields and the magnetospheric structure and coupling, of both components of hot and cool close binary systems over a significant range of evolutionary stages. Our results will confront current theories and trigger new ones, with the aim of qualitatively improving our understanding of the complex interplay between stellar magnetism and binarity.

Magnetic Topologies of Young Stars & the Survival of close-in massive Exoplanets (MaTYSSE)

PI: Donati

Instrument: ESPaDOnS. 478 hours, spread over 8 semesters.


MaTYSSE is a large program addressing major unsolved issues regarding the formation of Sun-like stars and their planetary systems, and in particular about the strong impact of magnetic fields on these initial steps so critical for our understanding of the early life of a star like our Sun. More specifically, MaTYSSE aims at studying the large-scale magnetic topologies of a sample of low- mass protostars that have mostly dissipated their accretion disc already (called weak-line T Tauri stars / wTTSs or transitional T Tauri stars / tTTSs) to investigate how different they are from those of protostars that are still surrounded by their accretion discs (called classical T Tauri stars / cTTSs), and from those of mature main-sequence stars; being the missing link in our knowledge of magnetic topologies of low-mass stars, tTTSs/wTTSs should reveal the kind of magnetospheres with which Sun-like stars initiate their unleashed spin-up as they contract towards the main-sequence. Through this survey, MaTYSSE will also be able to assess whether close-in giant planets (called hot Jupiters(hJs) are significantly more frequent around low-mass protostars than around mature stars and whether magnetospheric gaps can explain the survival of hJs around Sun-like stars. MaTYSSE also aims at monitoring a few selected cTTSs to document the long-term variation of their magnetic large-scale topologies and investigate how these variations are likely to affect magnetospheric gaps and the survival of hJs. By coupling together studies of magnetic fields of protostars and searches for young exoplanets, MaTYSSE should also ensure that scientists from the CFHT community are well prepared for exploiting SPIRou when the instrument comes on-line. MaTYSSE will also contribute to the MagIcS spectropolarimetric LEGACY survey.

History of the Magnetic Sun.

PI: Petit

Instrument: ESPaDOnS. 215.8 hours, spread over the 15A to 16B semesters.


Magnetic fields have been shown to have a crucial impact on star formation and evolution, activity, angular momentum evolution, and interaction with protoplanetary disks and short period exoplanets. While a wealth of data have been obtained on pre-main sequence, main sequence, and giant stars, we are still missing an understanding of how magnetic properties evolve with time from the PMS to the late-MS. The aim of the present Large Program is to bridge the gap between early PMS stars (1-5 Myr) and mature MS stars (2-5 Gyr), by deriving the magnetic topologies of young solar analogues in open clusters that sample the age range from 20 Myr to 600 Myr. We will thus trace the Magnetic History of the Sun. The datasets to be obtained will allow us to investigate the behavior of stellar dynamos as a function of age, rotation and depth of the convective zone as these young suns evolve from the PMS to the MS. Comparing the magnetic properties of early suns to those of mature ones, we will identify the critical parameters involved in dynamo field generation, including the strong rotational shear at the tachocline predicted by angular momentum evolution models.