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The 4MOST Hemisphere Survey (4HS) is a collaboration of 100+ researchers spanning 6 continents, with the shared goal of measuring optical spectra and redshifts for approx. 5 million galaxies across the entire southern sky, and with including high and unbiased completeness for galaxies at z < 0.15 -- hink GAMA-like depth and data quality over ~200x the area. The headline science goals for 4HS include measuring the cosmological growth rate of structure (including the action of gravity on the very largest scales) and to map galaxy demographics as a function of local and large-scale environment to resolve the aspects of `nature’ that are most significant in the process of galaxy formation and evolution. In combination with the next generation of wide area surveys -- including VRO-LSST, Euclid, SPHEREx, and ASKAP/MeerKAT/SKA -- the result is a dataset with exceptional legacy value, with broad and lasting scientific impact. In this talk, I will review the motivation and survey design for 4HS, including our data release plans. Along the way, i will also highlight some of my personal motivations for pursuing 4HS, including: measuring the galaxy luminosity function down to the Globular Cluster scale, new science opportunities for weak gravitational lensing, and tests of the cosmological principle. |
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