Intensity mapping of the atomic carbon [CII] line in post-reionization and reionization epoch with CONCERTO

Séminaire IPAG de Guilaine Lagache (LAM), jeudi 18 mai 2017 à 11h00, IPAG seminar room

The fine structure line [CII] at 158 microns is one of the brightest emission lines in the spectra of galaxies. It is considered to be the dominant coolant for neutral atomic gas in the interstellar medium. Conveniently, [CII] is redshifted into the sub-millimeter and millimeter atmospheric windows for 4.56). However, so far, [CII] studies of very distant galaxies have been limited, with detection of only a handful of galaxies. The full power of ALMA will revolutionize the field, detecting [CII] in individual galaxies in the heart of the reionization era. However, while ALMA will probably follow-up hundreds of high-redshift galaxies, its small field of view and narrow bandwidth will strongly limit its sensitivity/efficiency to conduct large unbiased spectral line surveys.

Rather than detecting [CII] in selected galaxies, we propose to map in 3-D the intensity due to the [CII] line emission, a technique known as Intensity Mapping. This technique measures signal fluctuations produced by the combined emission of the galaxy population on large regions of the sky in a wide frequency (thus redshift) band, and thus increases sensitivity to faint sources. I will discuss how [CII] intensity mapping measurements can offer a straightforward alternative for tracing the large structure of galaxies at z>4.5. By measuring [CII] fluctuations, I will show how we can obtain unprecedented constraints on star formation and dust build-up at a key epoch in the Universe. I will also discuss how cross-correlation of the signals (e.g. [CII] and galaxy surveys), as well as the lower redshift (z<2) CO-line fluctuations, could be used to further understand the physics of galaxy formation and reionization. Finally I will present the CONCERTO experiment, a [CII] spectrometer capable of covering few square degrees with a high sensitivity and proposed as a new intensity mapping experiment. Our instrument would be an invaluable opportunity for the APEX collaboration and the ESO community. In addition to the main [CII] survey, we expect CONCERTO to bring a significant contribution in a number of areas, including the study of galaxy clusters and the follow-up of Herschel and SCUBA-2 deep surveys.