[CII] is one of the brightest emission lines in the spectra of galaxies, and one of the most valuable tracers of dusty star formation at high redshift.

Redshifts z~5-8 marks an important epoch when the interstellar medium (ISM) in typical galaxies matures from a nearly primordial, dust-free state at z~8 to the dust- and metallicity-enriched state observed at z~4. Our knowledge of galaxies together with their interstellar medium at this epoch is almost exclusively based on rest-frame UV continuum. Complementary probes, such as CONCERTO, are thus absolutely essential.

We conducted with CONCERTO a survey of about 1.4 square degrees with about 800 hours of observing time, on the COSMOS field. The survey is providing a spatial-spectral data cube in which intensity is mapped as a function of sky position and redshift. The 3-D fluctuations will be studied in Fourier space with the power spectrum.