A pilot survey of star-forming galaxies at z = 6 with NOEMA.

Characterizing the properties of massive galaxies in the early universe is crucial for understandinggalaxy formation and evolution. One of the key open questions is how these galaxies were able tobuild their large dust reservoirs so early in the Universe, and what the physical conditions of theirinterstellar medium were. To address this challenge, we are conducting a survey with the NorthernExtended Millimeter Array (NOEMA) of six typical star-forming galaxies at z≈6, when the Universewas only 1 Gyr old. We detect these galaxies in the [CII] 158 μm transition—the main coolant of thecold neutral medium—and in the dust continuum. Our measurements show a ratio between the [CII] line and the far-infrared luminosity (FIR), [CII]/FIR, that is comparable to those measured in localstarbursts, suggesting similar conditions in their interstellar medium. One of the galaxies in oursample reveals extended [CII] line emission, allowing us to analyze the kinematics of the disk, whichsuggests regular rotation.