Abstract

We present the data release of the Lyα Tomography IMACS Survey (LATIS), one of the largest optical spectroscopic surveys of faint high-redshift galaxies. The survey provides 7408 optical spectra of candidate z ∼ 2–3 galaxies and QSOs in the Canada–France–Hawaii Telescope Legacy Survey D1, D2 (COSMOS), and D4 fields. The R ∼ 1000 spectra were obtained using the Inamori Magellan Areal Camera and Spectrograph (IMACS) at the Magellan Baade telescope, with typical integrations of 12 hr. From these spectra, we measured 5575 high-confidence spectroscopic redshifts, of which 4176 are at z > 1.7, thereby substantially increasing the number of public spectroscopic redshifts at z ≈ 2–3 in COSMOS and the other survey fields. The data release includes Lyα transmission fluctuations measured in 4.7 × 105 pixels, which were used to create 3D maps of the intergalactic medium (IGM) transmission spanning 1.65 deg2 and z = 2.2–2.8 at a resolution of 4 h −1 cMpc. These are the largest such maps to date and provide a novel tracer of large-scale structure in legacy fields. We also provide ancillary data, including mock surveys. The LATIS data will enable a variety of community studies of galaxy evolution, environments, and the IGM around cosmic noon. © 2025. The Author(s). Published by the American Astronomical Society.