PRIMA: Constraining the Infrared Spectral Energy Distribution of galaxies and AGN host galaxies with PRIMAger

Although numerous studies using Spitzer, Herschel, WISE, SOFIA, and ALMA (among others) have put constraints on the infrared (IR) spectral energy distribution (SED) of galaxies, the 20-100 microns range still lacks of strong observational constraints as shown by the wide disparity in IR SED models/libraries in this range (e.g., Ciesla et al. 2014). This domain is key to investigate the hidden star formation activity of galaxies but also to correctly disentangle IR emission due to star formation from the contribution of an active galactic nucleus (AGN). Indeed, the luminosity from 20-100 microns rest frame in galaxies accounts for the majority of the total IR luminosity, a lack of constraints in this range result in significant uncertainties in the IR luminosity density from galaxies over cosmic time. Large uncertainties on the IR SED of the host galaxies yields to large uncertainties on the contribution of the AGN and therefore on the estimate of its activity.

The only step forward to reach a consensus on this will be brought by PRIMA, a cryogenically-cooled, IR observatory for the community for the next decade. PRIMAger, onboard PRIMA, is an imager covering the IR domain from 25 to 260 microns. The 25-80 microns range will be covered by a set of 12 medium band filters (R~10) while the longer range will be covered by 4 broad bands with polarimetric capabilities. PRIMAger's capabilities will be a game changer to constrain the IR SED of galaxies and the activity of their super massive black holes.