SLIDE 7 Il devient alors possible d’effectuer des relevés cosmologiques avec des instruments de plus petites The 21cm observation at high redshifts (z ~ 6-15) has attracted great interest among astrophysicists and cosmologists in the last 15-20 years. Several on-going experiments are attempting to observe the 21cm signal originating from the epoch of reionization (EOR), at redshift 6-15, when the hydrogen gas was reionized by the high energy photons (UV, X) emitted by the first stars, galaxies and quasars. LOFAR in Europe, MWA (Australia/USA), PAPER (South Africa/USA), HERA (South Africa/USA), 21CMA (China), and GMRT (India) are the main projects searching for the EoR signals. Some of these instruments, LOFAR and MWA in particular are among the SKA (Square Km Array) pathfinders. More recently, since 10 years, 21 cm Intensity Mapping has been proposed as a an innovative method to carry cosmological surveys, at lower redshifts (z ~1-3) to help answering fundamental questions such as the nature of the Dark Energy component of the universe. Indeed, mapping the universe in radio through the observation of the 21 cm emission of the neutral hydrogen is a complementary approach to that of the optical surveys to study Large Scale Structures (LSS) and the BAO’s, in the redshift range z <~ 3, or maybe even up to redshift z <~ 6. Intensity mapping correspond to the
- bservation of total 21 cm emission from hundreds of galaxies, contained in cosmic cells of ~ 1000
Mpc^3, instead of detecting 21 cm emission from individual sources. Carrying cosmological through 21 cm Intensity Mapping becomes then possible using radio instruments with smaller collecting area and lower resolution, compared to SKA or FAST. Several instruments have been build or are planned to explore the intensity mapping method. The CHIME instrument in Canada features 3 large cylindrical reflectors, while two instruments have been built at the TIANLAI site in the Xinjiang province, in western China. One instrument has a design similar to CHIME, with 3 cylindrical defectors and a second instrument, a dish array with 16 6-meter reflectors. The HIRAX project (South Africa) plan to build a large dish array, with few hundred dishes, while BINGO will feature a single large reflector equipped with multi-feed receiver. The Tianlai instrument design has been carried by a an international collaboration, including US and french scientists, who are also involved also in the data
- analysis. The intensity mapping is also considered for the SKA mid-frequency instrument, despite a
non optimal instrument configuration. The SKA dish array would not be used in this cas in interferometric mode. We plan to organise a consortium with European partners (France, Italy, Switzerland, UK) and international partners (China, US) to study the scientific reach of Intensity mapping, the synergies with optical surveys, such as LSST, DESI and Euclid and submit a Horizon 2020 DS (Design Study) proposal to support these activities. This ANR proposal aims and of getting the financial support necessary to create the network of partners, design the work packages, submit the proposal and contribute to raise the community interest in this subject, and in the SKA project. projet est retenu pour financement (sous réserve d’une mise à jour si besoin). En déposant un dossier,
