Prospects for Observing Galaxy Spectral Energy Distribution from the Radio to the Far-infrared in the Era of Next-generation Radio Telescopes

The superb sensitivity and angular resolution of the next-generation radio telescopes with combined frequency coverage of approximately over 3 orders of magnitude (100 MHz–100 GHz) will sample the radio and far-infrared (FIR) spectral energy distribution (SED) of galaxies and revolutionize the galaxy formation study at the epoch of reionization and beyond. We present a prospect of observing the radio–FIR continuum SEDs of galaxies in the redshift of up to z ≈ 20 based on an ensemble of the simulated “energy balanced” panchromatic SED (from UV to FIR) extended to the radio. For “realistic” populations of UV star-forming galaxies and dusty star-forming galaxies (DSFGs), we simulate their SEDs by accounting for the CMB effect and the radio-IR correlation. The flux density evolution of the UV-bright star-forming galaxies and the DSFGs at the selected observing frequencies covered by the current (ALMA) and next generation (SKA and ngVLA) radio-millimeter telescopes, suggest that massive galaxies ( M * ≳ 10 10 M ⊙ ) are detectable at any redshift (0 < z < 20) in high frequency ( ν > 90GHz). In particular, when operating, the ngVLA high-frequency (≈100 GHz) band is capable of detecting galaxies with M * ≳ 10 9 M ⊙ almost independently from redshift and the SKA low-frequency observing window (≲1 GHz) has sufficient sensitivity to detect M * ≳ 10 10 M ⊙ DSFGs up to the epoch of reionization ( z = 5 ∼ 7). We also show that the brightness of anomalous microwave emission (AME) in the galaxy SED is insignificant if the galaxies are beyond the local Universe (e.g., z ≳ 0.1).