Nebular and Stellar Dust Extinction Across the Disk of Emission-Line
  Galaxies on Small (KPC) Scales
  We investigate resolved kpc-scale stellar and nebular dust distribution in
eight star-forming galaxies at z~0.4 in the GOODS fields. Constructing the
observed Spectral Energy Distributions (SEDs) per pixel, based on seven bands
photometric data from HST/ACS and WFC3, we performed pixel-by-pixel SED fits to
population synthesis models and estimated small-scale distribution of stellar
dust extinction. We use Halpha / Hbeta nebular emission line ratios from
Keck/DEIMOS high resolution spectra at each spatial resolution element to
measure the amount of attenuation faced by ionized gas at different radii from
the center of galaxies. We find a good agreement between the integrated and
median of resolved color excess measurements in our galaxies. The ratio of
integrated nebular to stellar dust extinction is always greater than unity, but
does not show any trend with stellar mass or star formation rate. We find that
inclination plays an important role in the variation of the nebular to stellar
excess ratio. The stellar color excess profiles are found to have higher values
at the center compared to outer parts of the disk. However, for lower mass
galaxies, a similar trend is not found for the nebular color excess. We find
that the nebular color excess increases with stellar mass surface density. This
explains the absence of radial trend in the nebular color excess in lower mass
galaxies which lack a large radial variation of stellar mass surface density.
Using standard conversions of star formation rate surface density to gas mass
surface density, and the relation between dust mass surface density and color
excess, we find no significant variation in the dust to gas ratio in regions
with high gas mass surface densities, over the scales probed in this study.
