Black hole accretion, star formation, and chemical evolution with PRIMA/FIRESS spectroscopy: toward the cosmic noon and beyond (2509.06954v1)

Abstract: The PRobe far-Infrared Mission for Astrophysics (PRIMA) will deliver the first comprehensive view of the obscured side of star formation and black hole accretion that dominates galaxy growth at cosmic noon. Around 90% of UV/optical photons from young stars and Active Galactic Nuclei (AGN) are absorbed by dust and reradiated in the mid- to far-infrared, where key diagnostic lines trace accretion, star formation, and the physical and chemical conditions of galaxies. PRIMA will conduct blind spectroscopic surveys out to $z \sim 3-4$, enabling an unbiased determination of the co-evolution of star formation and black hole growth with cosmic time. We simulate a 200 arcmin$^2$ blind spectroscopic survey with FIRESS to measure star formation and black hole accretion rates for hundreds of galaxies at cosmic noon. Follow-up observations will provide relative N/O abundances and N/O-independent metallicities from multiple mid-IR lines. In its high-resolution mode, FIRESS will probe feedback processes through P-Cygni profiles, blueshifted OH absorption, and emission-line wings from highly ionised gas. Beyond cosmic noon, PRIMA will pioneer rest-frame mid-IR spectroscopy of galaxies during reionisation. Bright high-ionisation lines will constrain the primary ionising continuum of luminous Lyman-$\alpha$ emitters and low-metallicity AGN, revealing the conditions that shaped the first galaxies and black holes. By bridging the gap between optical and radio facilities, PRIMA will deliver an unobscured, end-to-end view of the processes driving galaxy evolution from the earliest epochs to the peak of activity.