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Nebular and stellar dust extinction across the disk of emission-line galaxies on kiloparsec scales

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  • Shoubaneh Hemmati
  • Bahram Mobasher
  • Behnam Darvish
  • Hooshang Nayyeri
  • David Sobral
  • Sarah Miller
Article number46
<mark>Journal publication date</mark>20/11/2015
<mark>Journal</mark>The Astrophysical Journal
Issue number1
Number of pages10
Publication StatusPublished
<mark>Original language</mark>English


We investigate the resolved kiloparsec-scale stellar and nebular dust distribution in eight star-forming galaxies at z similar to 0.4 in the Great Observatories Origins Deep Survey fields. This is to get a better understanding of the effect of dust attenuation on measurements of physical properties and its variation with redshift. Constructing the observed spectral energy distributions (SEDs) per pixel, based on seven bands of photometric data from Hubble Space Telescope/Advanced Camera for Surveys and WFC3, we performed pixel-by-pixel SED fits to population synthesis models and estimated the small-scale distribution of stellar dust extinction. We use H alpha/H/beta 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 centers 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 (SFR). 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 SFR 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.