3D-HST

3D-HST is a near-infrared spectroscopic survey with the Hubble Space Telescope designed to study the physical processes that shape galaxies in the distant Universe. This Treasury program was allocated 248 orbits of HST time during Cycles 18 and 19, surveying ~600 square arcminutes of well-studied extragalactic survey fields (AEGIS, COSMOS, GOODS-S, UKIDSS-UDS) with two orbits of primary WFC3/G141 grism coverage and two to four orbits with ACS/G800L coverage. 3D-HST now provides the critical third dimension - redshift - for ~10,000 galaxies at z>1. This is the epoch when ~60% of the star formation in the Universe took place, the number density of quasars peaked, the first galaxies stopped forming stars and the structural regularity that we see in galaxies today emerged. The survey is optimally designed for the study of galaxy evolution over 1 < z < 3.5. The science objectives include: disentangling the processes that regulate star-formation in massive galaxies, evaluating the role of environment and mergers in shaping the galaxy population, and resolving the growth of disks and bulges, spatially and spectrally.