Polycyclic Aromatic Hydrocarbons (PAHs) in the High-redshift Universe: Prospect of the PRIMA FIRESS low-resolution spectroscopy

Abstract

The integrated luminosity from the features of the polycyclic aromatic hydrocarbons (PAHs) exceeds the luminosity from atomic and molecular emission lines in the star-forming regions in galaxies and is a potential tracer of galaxy-scale star formation and molecular gas content of the high-redshift universe. We simulate the observable PAH spectra using the PRobe far-Infrared Mission for Astrophysics far-infrared enhanced survey spectrometer (FIRESS) and investigate the capability of the FIRESS low-resolution spectroscopy for observing PAH emission spectrum from high-redshift galaxies. Our investigation suggests that (1) PRIMA observations of PAH emission are $\gtrsim 10$ times more efficient at detecting galaxies than the VLA observations of CO(1-0) for galaxies with the same infrared luminosity, (2) PRIMA/FIRESS can detect the PAH emission from galaxies with $L_{IR}\sim 10^{12}{L}_{\odot }$ up to the end of reionization (and possibly beyond, if $L_{IR}\sim 10^{13}{L}_{\odot }$), (3) the PAH band ratios measured from a full spectral fitting and from a simple flux "clipping" method are different and vary depending on the interstellar radiation field strength, and (4) PRIMA/FIRESS can also be used as the PAH mapping instrument to measure star formation and redshift of the galaxies in high-redshift protoclusters.

Comments: This paper is part of the JATIS special issue focused on the PRobe Infrared Mission for Astrophysics (PRIMA) probe mission concept. The issue is edited by Matt Griffin and Naseem Rangwala (JATIS VOL. 11, NO. 3 | July 2025)