Hierarchical Star Formation in Nearby LEGUS Galaxies

Abstract

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 7 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.

9 pages, 4 figures, accepted for ApJL

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Cited by in corpus (23)

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• The Spatial Relation between Young Star Clusters and Molecular Clouds in M 51 with LEGUS
• Cloud Structure of Galactic OB Cluster Forming Regions from Combining Ground and Space Based Bolometric Observations
• Hierarchical Star Formation in Turbulent Media: Evidence from Young Star Clusters
• The VMC Survey XXII. Hierarchical Star Formation in the 30 Doradus-N158-N159-N160 Star-Forming Complex
• The SAMI Galaxy Survey: The discovery of a luminous, low-metallicity H II complex in the dwarf galaxy GAMA J141103.98-003242.3
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• The Dynamics and Distribution of Angular Momentum in HiZELS Star-Forming Galaxies at z = 0.8 - 3.3
• Spatially Resolved Dust, Gas, and Star Formation in the Dwarf Magellanic Irregular NGC4449
• The Dependence of the Hierarchical Distribution of Star Clusters on Galactic Environment
• HST imaging of star-forming clumps in 6 GASP ram-pressure stripped galaxies
• Understanding formation of young, distributed low-mass stars and clusters in the W4 cloud complex
• The VMC Survey XXVII. Young Stellar Structures in the LMC${}^{\prime }$s Bar Star-Forming Complex
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• A Comparative Study of Star Forming Dwarf Galaxies using the UVIT
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• A FUV-optical approach for studying hierarchical star formation in nearby galaxies with UVIT
• Investigating the young stellar populations and hierarchies in nearby galaxies with the UVIT. II. Presenting the properties of ~25,000 UV-detected star-forming clumps