CONCERTO · Intensity mapping of the atomic carbon CII line: the promise of a new observational probe of dusty star-formation in post-reionization and reionization epoch

I propose for funding to construct a spectrometer to map in 3-D the intensity due to line emission, atechnique known as Intensity Mapping. Instead of detecting individual galaxies, this emerging techniquemeasures signal fluctuations produced by the combined emission of the galaxy population on large regionsof the sky in a wide frequency (i.e. redshift) band, and thus increases sensitivity to faint sources.Capitalizing on a recent technology breakthrough, our intensity mapping experiment will measure the 3-Dfluctuations of the [CII] line at redshifts 4.5<z<8.5. [CII] is one of the most valuable star formation tracersat high redshift. My project will answer the outstanding questions of whether dusty star-formationcontributes to early galaxy evolution, and whether dusty galaxies play an important role in shaping cosmicreionization.My team will first build, test, and finally install the instrument on the APEX antenna following anagreement with APEX partners. The spectrometer will be based on the state-of-the-art development of newarrays in the millimeter using Kinetic Inductance Detectors. Spectra (200-360 GHz) will be obtained by afast Martin-Puplett interferometer. Then, we will observe with CONCERTO a few square degrees and offera straight forward alternative for probing star formation and dust build-up in the early Universe. Finally,CONCERTO will set to music the various cosmic evolution probes. Cross-correlation of the signals will beused in particular to capture the topology of the end of reionization era.CONCERTO will be one of two instruments in the world to perform intensity mapping of the [CII] line inthe short term. The novel methodology is extremely promising as it targets an unexplored observabletouching on some of the fundamental processes building the early universe. In the flourishing of new ideasin the intensity-mapping field, CONCERTO lies at the forefront.