Hierarchical Star Formation in Nearby LEGUS Galaxies

Type Journal Article
Names Debra Meloy Elmegreen, Bruce G. Elmegreen, Angela Adamo, Alessandra Aloisi, Jennifer Andrews, Francesca Annibali, Stacey N. Bright, Daniela Calzetti, Michele Cignoni, Aaron S. Evans, John S., III Gallagher, Dimitrios A. Gouliermis, Eva K. Grebel, Dei
Publication The Astrophysical Journal Letters
Volume 787
Issue 1
Pages L15
Journal Abbreviation The Astrophysical Journal Letters
Date May 1, 2014
DOI 10.1088/2041-8205/787/1/L15
ISSN 0004-637X
URL http://adsabs.org/2014ApJ.787L.15E
Library Catalog adslabs.org
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 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.
Tags Galaxies: ISM, ISM: structure, STARS: FORMATION, galaxies: star clusters: general
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