UVIT Study of the Magellanic Clouds (U-SMAC). III. Hierarchical star formation in the Small Magellanic Cloud regulated by turbulence

The Small Magellanic Cloud (SMC), a satellite galaxy of the Milky Way, is an irregular dwarf galaxy exhibiting evidence of recent and ongoing star formation. We performed a spatial clustering analysis of far-ultraviolet stars in the SMC younger than 150 Myr using data from the Ultra Violet Imaging Telescope on board AstroSat. We identified 236 young stellar structures as surface overdensities at different significance levels. The sizes of these structures range from a few parsecs to several hundred parsecs. Their irregular morphologies are characterized by a perimeter-area dimension, derived from the projected boundaries of the young stellar structures, of D_p = 1.46 ± 0.4. The 2D fractal dimensions obtained from, respectively, the number-size relation and the size distribution are D₂ = 1.64 ± 0.03 and D₂ = 1.31 ± 0.16. These values indicate significant lumpiness among the young stellar structures. In addition, the surface density distribution of the identified structures follows a log-normal distribution. These features are strikingly similar to those of the turbulent interstellar medium, thus supporting the scenario of hierarchical star formation regulated by supersonic turbulence.