A New Hope for Obscured AGN: The PRIMA-NewAthena Alliance

Luigi Barchiesi, F. J. Carrera, C. Vignali, F. Pozzi, L. Marchetti, C. Gruppioni, I. Delvecchio, L. Bisigello, F. Calura, J. Aird, M. Vaccari

First listed 2025-03-25 | Last updated 2025-03-25

Abstract

Understanding the AGN-galaxy co-evolution, feedback processes, and the evolution of Black Hole Accretion rate Density (BHAD) requires accurately estimating the contribution of obscured Active Galactic Nuclei (AGN). However, detecting these sources is challenging due to significant extinction at the wavelengths typically used to trace their emission. We evaluate the capabilities of the proposed far-infrared observatory PRIMA and its synergies with the X-ray observatory NewAthena in detecting AGN and in measuring the BHAD. Starting from X-ray background synthesis models, we simulate the performance of NewAthena and of PRIMA in Deep and Wide surveys. Our results show that the combination of these facilities is a powerful tool for selecting and characterising all types of AGN. While NewAthena is particularly effective at detecting the most luminous, the unobscured, and the moderately obscured AGN, PRIMA excels at identifying heavily obscured sources, including Compton-thick AGN (of which we expect 7500 detections per deg$^2$). We find that PRIMA will detect 60 times more sources than Herschel over the same area and will allow us to accurately measure the BHAD evolution up to z=8, better than any current IR or X-ray survey, finally revealing the true contribution of Compton-thick AGN to the BHAD evolution.

Short digest

Simulation-driven forecast of a full obscured-AGN census using the far-IR PRIMA plus X-ray NewAthena, built on X-ray background synthesis models and Deep/Wide survey layouts. PRIMA dominates for heavily obscured and Compton-thick accretors, yielding an expected 7500 CT-AGN detections per square degree, while NewAthena preferentially recovers the most luminous, unobscured, and moderately obscured sources. Together they out-perform past IR efforts—PRIMA alone delivers ~60× Herschel source counts over the same area—and enable a precise BHAD history to z≈8. The alliance is pitched as the cleanest route to reveal the true CT-AGN contribution to cosmic BH growth.

Key figures to inspect

• Fig. 1 (PRIMA Deep, PPI1 at 98 um): Inspect the purple overlap versus red/blue regions across NH and Lx bins to see exactly where PRIMA+NewAthena deliver joint detections, and compare to the cross-hatched Herschel limits to quantify the gain over PACS.
• Fig. 2 (Deep survey photometric coverage): Use the color gradation (number of PRIMAger filters hit) to judge where full PHI+PPI coverage is routine versus sparse; this shows which NH–luminosity regimes will have robust IR SED decomposition and AGN/SF disentangling, and how many of those are also WFI-detected.
• Fig. 3 (Wide survey counts with PPI1): Check how surface-density expectations shift from Deep to Wide for each obscuration class and luminosity bin, highlighting where PRIMA alone secures CT statistics and where joint detections remain feasible.
• Fig. 4 (Wide survey photometric detections): Evaluate filter-by-filter completeness in the Wide tier; identify redshift windows where multi-band coverage is sufficient for BHAD estimates even without X-ray confirmation.