Simulations Find Our Accounting of Dust-Obscured Star Formation May Be
  Incomplete
  The bulk of the star-formation rate 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 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 UVJ 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 SED modeling that includes realistic SFHs and allows for
variable attenuation curves if we want to fully account for dust obscured
star-formation across the epochs of greatest galaxy build-up.
