The plethora of observations of the past decade, covering the entire electromagnetic spectrum, has initiated deep transformations in modern cosmology. The combination of space and ground-based data, of both wide and high-resolution surveys, led to repeated confirmations of the standard Big Bang model. The Universe is made for 25% of matter: 5% ordinary matter and 20% dark matter. The remaining 75% is a fluid of negative pressure, the so called dark energy, responsible for the acceleration of the expansion rate. But fundamental knowledge gaps remain, in particular concerning the formation of structures at all scales, from galaxies to large voids and filaments.
The combination of different cosmological surveys is essential in order to learn about the role of baryons in galaxy formation and to investigate some of the fundamental properties of nature such as the neutrino mass, the nature of dark matter or the validity of General Relativity at large scale. My research consists in developing new theoretical tools and use them on data to explore these questions. I use multi-wavelengths observations that probe the electromagnetic spectrum (e.g. PLANCK), and optical galaxy surveys to trace dark matter using the gravitational lensing effect. The combination of multi-wavelength surveys and dark matter from lensing is a very powerful and unique way to address fundamental questions about the Universe.
On-going optical galaxy surveys:
Canada France Hawaii Telescope Lensing Survey (CFHTLenS, PI):
CFHTLenS is the science team of the CFHT Legacy Survey (CFHTLS), it comprises ~20 researchers across the world from a dozen of different institutions. Other countries involved are the Netherlands, France, China, Taiwan, US and Germany. CFHTLenS produced a wealth of new results and delivered major technical breakthroughs for the measurement and analysis of lensing data. Its legacy value is immense, and it is paving the way for future studies of the dark universe (Euclid, LSST, DES). All data products are available form the CFHTLenS web pages (as well as from the Canadian Astronomy Data Center).
The Next Generation Virgo Survey (NGVS, CoI):
The Next Generation Virgo Cluster Survey (NGVS) is a large program for the Canada France Hawaii Telescope (CFHT). The data acquisition ended in 2013 and the science analysis is currently in progress. The NGVS is the state-of- the-art optical survey of a low-redshift cluster environment for years to come. The Virgo cluster of galaxies has been observed in four optical bands and it will offer a dramatic new perspective of cluster physics and environment. This project is an international collaboration with France, UK, US, Germany, Italy, the Netherland, China.
The Kilo Degree Survey (KiDS, CoI):
The Kilo Degree Survey (KiDS) isa new generation optical survey that will cover 1500 square degrees with 9 filter bands (from UV to near infrared). Data acquisition should be complete around 2017. This is a post CFHTLenS generation surveys. It will measure the dark matter/baryon relative distributions to high precision at various scales, from galaxies to the most massive cluster of galaxies. KiDS is an ESO public survey lead by the Netherlands. The lensing sub-team in an international collaboration beiging together many of the researchers from the Canada France Hawaii Telescope Lensing Survey (CFHTLenS).
The Red Cluster Sequence Lensing Survey (RCSLenS, CoI):
The RCSLenS team, formed after CFHTLenS, will perform the weak lensing analysis of RCS2 data using all the tools and expertise developed for CFHTLenS. The RCS2 survey is described here. The science topics are similar to those achieved with CFHTLenS, although the sky coverage is significantly larger. Data products and scientific results will be available from the RCSLenS web site in the near future.
The COnstrain Dark Energy with X-ray clusters (CODEX, Canadian PI)
CODEX is an optical survey targetting carefully selected clusters of galaxies in order to obtain their detailed characterization of the dark matter distribution, and compare it to the Xray and Sunyaev-Zeldovich data sets in order to learn about the baryon distribution and baryons physics. This is an internal collaboration with Finland, Brazil, Germany, UK, the Netherlands, US and France. The CODEX sample is unique by its overlap with Xray XMM data and SZ CARMA data.
The Canada France Hawaii Telescope Stripe 82 survey (CS82, Canadian PI)
The CFHT Stripe 82 survey (CS82) is an optical survey of the equatorial galactic plane, intended to perform lensing studies in a region of the sky that has been observed intensively with many other facilities at all wavelengths (the so called stripe 82). Data collection was completed in 2012 and the science analysis is under way. This project is a collaboration with Japan, Brazil, UK, Germany and the US. The synergistic dimension with other data sets, from radio to Xray energy range, is unique.
1996-2004: The discovery in 2000 (with three other competing teams) of gravitational lensing by large scale structure was performed on the VIRMOS-Descart imaging survey. Using data collected by the CFHT12K camera on the Canada France Hawaii Telescope, Thomas Erben (from MPA, Munich) and I (at the Canadian Institute for Theoretical Astrophysics) performed the science analysis that lead to the discovery, published here, and advertised by CFHT for the media here.
2005-2009: the Shear Testing Program (STEP) was an international initiative to address the difficult problem of accurate galaxy shape measurement in the context of gravitational lensing by large scale structure. It later evolved in STEP2 and tge GREAT challenges. STEP was coordinated by Catherine Heymans, former postdoc at UBC. One of the most important publications of the STEP project can be found here, with a STEP2 followup here.
2007-2011: The Dark Universe through Extragalactic Lensing (DUEL) was a European Community Research Training Network (6th framework), composed of researchers from across Europe and Canada, ran for four years from January 2007. The aims of DUEL was to exploit what was at that time imminent, large-scale imaging and multi- wavelength galaxy surveys and prepare for future gravitational lensing surveys. The analysis focussed on theoretical studies, simulations (STEP) and ground and spaced based data. Other countries involved were Germany, France, the Netherland, Italy, for a total of 9 coordinating nodes. I was the coordinator of the Canadian node. DUEL seeded the emergence of the CFHTLenS team. An incomplete list of DUEL publications can be found here.