COSMOS-3D: A Legacy Spectroscopic/Imaging Survey of the Early Universe

We propose to perform a slitless spectroscopic survey with NIRCam/WFSS targeting the COSMOS-Web field together with deep parallel MIRI imaging, to establish a treasury dataset covering the largest ever field (0.33 deg2, including 500 arcmin^2 with MIRI) in the infrared, and secure redshifts of ~20000 galaxies and 5000 AGN over a survey volume of 3x10^7 Mpc^3, including >4000 galaxies and up to 500 AGN at z>5, into the epoch of reionization (EoR), providing a true 3-D panoramic view of the early Universe and addressing the following key scientific questions:

(1) How did the early massive galaxies emerge? Do they pose a challenge to modern cosmology? We will measure unbiased 3-d galaxy correlation function at EoR to map the growth of early dark matter halos and unveil the earliest galaxy protoclusters.

(2) How did the early supermassive black holes (SMBHs) emerge? What is the nature of the puzzling 'Little Red Dots' unveiled by JWST? The survey will provide a complete AGN census in the early universe to probe the modes of early SMBH accretion and growth.

(3) How did 'Cosmic Web' of the Universe emerge? What's the sources of reionization? How did galaxies and SMBHs evolve in that context? The survey will produce the first IGM tomographic map at EoR and trace IGM/galaxy connections from cosmic noon to reionization.

This treasury dataset will enable a wide-range of extragalactic science, including the measurements of high-z galaxy luminosity function, census of dusty galaxies across cosmic time, supernovae and AGN detections through variability. The team will provide fully reduced spectra and valued added spectroscopic and photometric catalogs to the community.