Black hole accretion, star formation, and chemical evolution with PRobe far-infrared mission for astrophysics/far-IR enhanced survey spectrometer spectroscopy: toward the cosmic noon and beyond

The PRobe far-Infrared Mission for Astrophysics (PRIMA) will provide the first complete three-dimensional view of the hidden side of star formation and black hole accretion that dominate energy production in galaxies during the cosmic noon. Nearly 90% of UV/optical photons from young stars in galaxies and Active Galactic Nuclei (AGN) at cosmic noon are absorbed by dust and reradiated in the mid- to far-infrared (IR) range. The latter hosts a unique suite of diagnostic lines for tracing black hole accretion and star formation, and probing physical and chemical conditions in galaxies. PRIMA will conduct blind spectroscopic surveys out to z∼3−4, enabling the first statistically unbiased determination of star formation and black hole accretion co-evolution with cosmic time.We simulate a 200 arcmin2 blind spectroscopic survey with FIRESS to measure star formation and black hole accretion rates for hundreds of galaxies during cosmic noon. Follow-up observations of selected targets from this or other surveys will determine relative N/O abundances and N/O-independent metallicities using multiple mid-IR emission lines. Using FIRESS’s high-resolution mode, it will be possible to study feedback mechanisms by detecting P-Cygni profiles and blueshifted absorption wings in molecular lines such as OH, and through emission line wings of highly ionized gas.Beyond cosmic noon, PRIMA will pioneer rest-frame mid-IR spectroscopy of galaxies in the reionization epoch. Bright high-ionization lines in the mid-IR will provide a transformative view of the primary ionization continuum of bright Lyman-α emitters and low-metallicity AGN in the early Universe, revealing conditions that drove the first generations of galaxies and black holes. By filling a critical observational gap between optical and radio wavelengths left by existing and planned facilities, PRIMA will deliver a comprehensive and unobscured view of the processes governing galaxy evolution, from the earliest epochs to the peak of star formation activity.