Simulations Find Our Accounting of Dust-obscured Star Formation May Be Incomplete

The bulk of the star formation rate (SFR) density peak at cosmic noon was obscured by dust. How accurately we can assess the role of dust-obscured star formation is affected by inherent biases in our empirical methods-both those that rely on direct dust emission and those that rely on the inferred dust attenuation of starlight. We use a library of hydrodynamic simulations with radiative transfer to explore these biases. We find that for infrared (IR) luminous galaxies that are in rapidly quenching systems (e. g., post-coalescence), standard luminosity-to-SFR relations can strongly overestimate the true SFRs. We propose using the L-IR/L-1.6 color to both help identify such systems and provide more accurate SFRs. Conversely, we find that the diagnostic rest-frame U-V versus V-J (UVJ) color-color plot misidentifies a subset of dusty star-forming galaxies. This is due to variability in the effective attenuation curves, including being much grayer in the optical-to-near-IR regime than the Calzetti starburst law. This is in agreement with recent observations of IR-selected galaxies at cosmic noon. Our results support the view that we need a panchromatic approach from the rest-frame UV through the IR and spectral energy distribution modeling that includes realistic star formation histories and allows for variable attenuation curves if we want to fully account for dust-obscured star formation across the epochs of the greatest galaxy build-up.