How Well Can We Measure Galaxy Dust Attenuation Curves? The Impact of
  the Assumed Star-Dust Geometry Model in SED Fitting
  One of the most common methods for inferring galaxy attenuation curves is via
spectral energy distribution (SED) modeling, where the dust attenuation
properties are modeled simultaneously with other galaxy physical properties. In
this paper, we assess the ability of SED modeling to infer these dust
attenuation curves from broadband photometry, and suggest a new flexible model
that greatly improves the accuracy of attenuation curve derivations. To do
this, we fit mock SEDs generated from the Simba cosmological simulation with
the Prospector SED fitting code. We consider the impact of the commonly-assumed
uniform screen model and introduce a new non-uniform screen model parameterized
by the fraction of unobscured stellar light. This non-uniform screen model
allows for a non-zero fraction of stellar light to remain unattenuated,
resulting in a more flexible attenuation curve shape by decoupling the shape of
the UV attenuation curve from the optical attenuation curve. The ability to
constrain the dust attenuation curve is significantly improved with the use of
a non-uniform screen model, with the median offset in UV attenuation decreasing
from $-0.30$ dex with a uniform screen model to $-0.17$ dex with the
non-uniform screen model. With this increase in dust attenuation modeling
accuracy, we also improve the star formation rates (SFRs) inferred with the
non-uniform screen model, decreasing the SFR offset on average by $0.12$ dex.
We discuss the efficacy of this new model, focusing on caveats with modeling
star-dust geometries and the constraining power of available SED observations.
