Artist Illustration of Early-Universe Quasar Cosmic Neighborhood

Observations using the Department of Energy-fabricated Dark Energy Camera (DECam) on the U.S. National Science Foundation Víctor M. Blanco 4-meter Telescope confirm astronomers’ expectation that early-Universe quasars formed in regions of space densely populated with smaller companion galaxies. DECam’s exceptionally wide field of view and special filters played a crucial role in reaching this conclusion, and the observations reveal why previous studies seeking to characterize the density of early-Universe quasar neighborhoods have yielded conflicting results.