4MOST

The 4MOST Hemisphere Survey of the Nearby Universe (4HS) is an accepted ESO public survey to conduct a massive spectroscopic survey of the southern sky, obtaining spectroscopic redshifts up to 7.2 million galaxies. This will be achieved with very high (>95%) and unbiased completeness over 21,000 square degrees, and with a particular focus on the nearby Universe (z < 0.15). Hudson and Percival were co-Is on the 4HS proposal and are members of the scientific collaboration.   Hudson has two main interests in 4HS. 1) To use 4HS to reconstruct the large-scale structure in the Southern Hemisphere and compare predicted peculiar velocities with the Fundamental-Plane-based peculiar velocities that 4HS will measure. 2) To cross-correlate Euclid and Rubin weak lensing probes of dark matter with the 4HS redshifts to understand topics such as the galaxy-halo connection and its dependence on environment and the dark matter structures of galaxy group and cluster halos, filaments of the cosmic web and cosmic voids. Percival focuses particularly on galaxy surveys, using the positions of galaxies to measure the cosmological expansion rate and growth of cosmological structure. He uses these to constrain Dark Energy, the mechanism responsible for the present-day acceleration in the expansion rate.