Modeling Dust and Starlight in Galaxies Observed by Spitzer and
  Herschel: The KINGFISH Sample
  Dust and starlight are modeled for the KINGFISH project galaxies. With data
from 3.6 micron to 500 micron, models are strongly constrained. For each pixel
in each galaxy we estimate (1) dust surface density; (2) q_PAH, the dust mass
fraction in PAHs; (3) distribution of starlight intensities heating the dust;
(4) luminosity emitted by the dust; and (5) dust luminosity from regions with
high starlight intensity. The models successfully reproduce both global and
resolved spectral energy distributions. We provide well-resolved maps for the
dust properties. As in previous studies, we find q_PAH to be an increasing
function of metallicity, above a threshold Z/Z_sol approx 0.15. Dust masses are
obtained by summing the dust mass over the map pixels; these "resolved" dust
masses are consistent with the masses inferred from model fits to the global
photometry. The global dust-to-gas ratios obtained from this study correlate
with galaxy metallicities. Systems with Z/Z_sol > 0.5 have most of their
refractory elements locked up in dust, whereas when Z/Z_sol < 0.3 most of these
elements tend to remain in the gas phase. Within galaxies, we find that q_PAH
is suppressed in regions with unusually warm dust with nu L_nu(70 um) >
0.4L_dust. With knowledge of one long-wavelength flux density ratio (e.g.,
f_{160}/f_{500}), the minimum starlight intensity heating the dust (U_min) can
be estimated to within ~50%. For the adopted dust model, dust masses can be
estimated to within ~0.07 dex accuracy using the 500 micron luminosity nu
L_nu(500) alone. There are additional systematic errors arising from the choice
of dust model, but these are hard to estimate. These calibrated prescriptions
may be useful for studies of high-redshift galaxies.
