About the project

CONCERTO stands for CarbON [CII] line in post‑rEionisation and ReionisaTiOn. The primary goal of the CONCERTO project is to map [C II] 158 µm line intensity fluctuations from redshifts z ≃ 4.5 to 8.5, corresponding to the end of the Reionization Era and post‑reionization epoch

CONCERTO employs line intensity mapping (LIM) to statistically measure the combined emission from faint, unresolved dusty, star-forming galaxies—allowing a census of early-universe star formation without relying on detecting individual objects.

The instrument was deployed on the 12m APEX telescope at ∼5100 m altitude in Chile's Atacama Desert. It used a dilution cryostat cooling system to ∼70 mK, with two focal planes comprising some ~4300 Kinetic Inductance Detectors (KIDs), delivering a large instantaneous Field-of-View of ~18.6 arcmin diameter and spectral resolution up to 1.5 GHz. Spectra were acquired via a fast Martin–Puplett Fourier transform spectrometer (FTS), allowing rapid integration across all pixels and continuous sky scanning. Installation and commissioning began in April 2021, with scientific [C II] survey operations launching in July 2021 and concluding before CONCERTO's removal, necessitated by ESO's scheduled withdrawal from APEX at the end of 2022.

Our experiment was also designed to observe star-forming regions from our Galaxy and the CO intensity fluctuations arising from 0.3 < z < 2 galaxies, giving the spatial distribution and abundance of molecular gas over a broad range of cosmic time. To have a look to other science goals than [CII] intensity mapping, click on one of the 4 icons below.

Data reduction of the large [C II] survey is currently underway — results will be shared soon. In the meantime, see our publications page for results from other science topics.

CONCERTO was mostly founded by the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No 788212). The ERC ended in June 2025. The project also received support from the Excellence Initiative of Aix-Marseille University (A*Midex), a French “Investissements d’Avenir” programme, and the Labex FOCUS.

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