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Title: HIERARCHICAL STAR FORMATION IN NEARBY LEGUS GALAXIES

Hierarchical structure in ultraviolet images of 12 late-type LEGUS galaxies is studied by determining the numbers and fluxes of nested regions as a function of size from ∼1 to ∼200 pc, and the number as a function of flux. Two starburst dwarfs, NGC 1705 and NGC 5253, have steeper number-size and flux-size distributions than the others, indicating high fractions of the projected areas filled with star formation. Nine subregions in seven galaxies have similarly steep number-size slopes, even when the whole galaxies have shallower slopes. The results suggest that hierarchically structured star-forming regions several hundred parsecs or larger represent common unit structures. Small galaxies dominated by only a few of these units tend to be starbursts. The self-similarity of young stellar structures down to parsec scales suggests that star clusters form in the densest parts of a turbulent medium that also forms loose stellar groupings on larger scales. The presence of super star clusters in two of our starburst dwarfs would follow from the observed structure if cloud and stellar subregions more readily coalesce when self-gravity in the unit cell contributes more to the total gravitational potential.
Authors:
 [1] ;  [2] ; ;  [3] ; ; ; ; ;  [4] ; ;  [5] ;  [6] ; ;  [7] ;  [8] ;  [9] ;  [10] ;  [11] ;  [12] ;  [13] more »; « less
  1. Vassar College, Department of Physics and Astronomy, Poughkeepsie, NY 12604 (United States)
  2. IBM Research Division, T.J. Watson Research Center, Yorktown Hts., NY 10598 (United States)
  3. Max Planck Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany)
  4. Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)
  5. Department of Astronomy, University of Massachusetts, Amherst, MA 01003 (United States)
  6. INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)
  7. Department of Astronomy, University of Virginia, P.O. Box 400325, Charlottesville, VA 22904-4325 (United States)
  8. Department of Astronomy, University of Wisconsin-Madison, WI 53706 (United States)
  9. Astronomisches Rechen-Institut, Zentrum für Astronomie der Universität Heidelberg, Mönchhofstr. 12-14, D-69120 Heidelberg (Germany)
  10. Lowell Observatory, 1400 West Mars Hill Road, Flagstaff, AZ 86001 (United States)
  11. School of Earth and Space Exploration, Arizona State University, Tempe, AZ 85287 (United States)
  12. Space Telescope Science Institute and European Space Agency, Baltimore, MD 21218 (United States)
  13. Department of Physics and Astronomy, Johns Hopkins University, 3701 San Martin Drive, Baltimore, MD 21218 (United States)
Publication Date:
OSTI Identifier:
22365834
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astrophysical Journal Letters; Journal Volume: 787; Journal Issue: 1; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; GALAXIES; GRAVITATION; IMAGES; POTENTIALS; STAR CLUSTERS; STAR EVOLUTION; STARS; ULTRAVIOLET RADIATION