Unveiling the Origin of Fast Radio Bursts by Modeling the Stellar Mass and Star Formation Distributions of Their Host Galaxies

Abstract Diverse formation channels have been proposed to explain the emergence of fast radio bursts (FRBs), yet their origin remains elusive. With improved localization precision, roughly 90 FRBs are now associated with host galaxies. Spectral energy distribution fitting to the host galaxy photometry reveals their stellar masses ( M ⋆ ) and star formation rates (SFRs), enabling discrimination between various formation channels. We conduct an extensive comparison of the stellar mass, SFR, and redshift distributions of 51 FRB hosts and mock generated galaxy samples to test whether FRBs trace SFR or M ⋆ . We incorporate a mass-to-light ratio ( ( M ⋆ / L r ) obs ) prescription to address optical selection biases. In line with K. Sharma et al., we provide evidence in favor of FRB progenitors tracking SFR rather than stellar mass. We show that the shape of the assumed ( M ⋆ / L r ) o b s distribution affects the predictions, bringing the low-mass end of the stellar mass distribution closer to the data when accounting for the SFR – ( M ⋆ / L r ) obs correlation. The K -correction effect in the r band is minimal for galaxies at z ≲ 0.7. In the model in which FRBs trace SFR, up to ∼6% of a flux-limited FRB host sample can reside below the star-forming main sequence. Finally, we examine a hybrid model in which a fraction of FRBs tracks stellar mass rather than SFR. This fraction can be as large as ∼40%−50%, suggesting that multiple formation channels are still consistent with observations. The toolkit developed in this work, GALFRB ( https://github.com/loudasnick/GALFRB ; N. Loudas et al.), is publicly available, offering a straightforward way to generate mock galaxy samples suitable for direct comparisons with future FRB host galaxy data.