Non-Blackbody Disks Can Help Explain Inferred AGN Accretion Disk Sizes
  If the atmospheric density $\rho_{atm}$ in the accretion disk of an active
galactic nucleus (AGN) is sufficiently low, scattering in the atmosphere can
produce a non-blackbody emergent spectrum. For a given bolometric luminosity,
at ultraviolet and optical wavelengths such disks have lower fluxes and
apparently larger sizes as compared to disks that emit as blackbodies. We show
that models in which $\rho_{\rm atm}$ is a sufficiently low fixed fraction of
the interior density $\rho$ can match the AGN STORM observations of NGC 5548
but produce disk spectral energy distributions that peak at shorter wavelengths
than observed in luminous AGN in general. Thus, scattering atmospheres can
contribute to the explanation for large inferred AGN accretion disk sizes but
are unlikely to be the only contributor. In the appendix section, we present
unified equations for the interior $\rho$ and $T$ in gas pressure-dominated
regions of a thin accretion disk.
