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

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. This work simulate the observable PAH spectra using the PRIMA Far-Infrared Enhanced Survey Spectrometer (FIRESS) and investigates 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 ≳ 10 times more efficient at detecting galaxies than the VLA observations of CO(1-0) for galaxies with the same IR luminosity, (2) PRIMA/FIRESS can detect the PAH emission from galaxies with LIR ∼ 1012 L⊙ up to the end of reionization (and possibly beyond, if LIR ∼ 1013 L⊙), (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.