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Title: EXTINCTION AND DUST GEOMETRY IN M83 H II REGIONS: AN HUBBLE SPACE TELESCOPE/WFC3 STUDY

We present Hubble Space Telescope/WFC3 narrow-band imaging of the starburst galaxy M83 targeting the hydrogen recombination lines (Hβ, Hα, and Paβ), which we use to investigate the dust extinction in the H II regions. We derive extinction maps with 6 pc spatial resolution from two combinations of hydrogen lines (Hα/Hβ and Hα/Paβ), and show that the longer wavelengths probe larger optical depths, with A{sub V} values larger by ≳1 mag than those derived from the shorter wavelengths. This difference leads to a factor ≳2 discrepancy in the extinction-corrected Hα luminosity, a significant effect when studying extragalactic H II regions. By comparing these observations to a series of simple models, we conclude that a large diversity of absorber/emitter geometric configurations can account for the data, implying a more complex physical structure than the classical foreground ''dust screen'' assumption. However, most data points are bracketed by the foreground screen and a model where dust and emitters are uniformly mixed. When averaged over large (≳100-200 pc) scales, the extinction becomes consistent with a ''dust screen'', suggesting that other geometries tend to be restricted to more local scales. Moreover, the extinction in any region can be described by a combination of the foreground screen and the uniformmore » mixture model with weights of 1/3 and 2/3 in the center (≲2 kpc), respectively, and 2/3 and 1/3 for the rest of the disk. This simple prescription significantly improves the accuracy of the dust extinction corrections and can be especially useful for pixel-based analyses of galaxies similar to M83.« less
Authors:
; ;  [1] ;  [2] ;  [3] ;  [4] ;  [5] ; ;  [6] ;  [7]
  1. Astronomy Department, University of Massachusetts, Amherst, MA 01003 (United States)
  2. Space Telescope Science Institute, Baltimore, MD 21218 (United States)
  3. Department of Physics and Astronomy, University of Toledo, Toledo, OH 43606 (United States)
  4. Astronomy Department, University of Virginia, P.O. Box 3818, Charlottesville, VA 22903 (United States)
  5. Center for Astrophysical Sciences, Johns Hopkins University, Baltimore, MD 21218 (United States)
  6. School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States)
  7. Galaxies Unlimited, Lutherville, MD 21093 (United States)
Publication Date:
OSTI Identifier:
22364111
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 778; Journal Issue: 2; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; ACCURACY; ASTRONOMY; ASTROPHYSICS; COMPARATIVE EVALUATIONS; CORRECTIONS; COSMIC DUST; GALAXIES; H2 REGIONS; HYDROGEN; INTERGALACTIC SPACE; LUMINOSITY; MIXTURES; RECOMBINATION; SPACE; SPATIAL RESOLUTION; TELESCOPES