UVIT Study of the Magellanic Clouds (U-SMAC). III. Hierarchical Star Formation in the Small Magellanic Cloud Regulated by Turbulence

TL;DR

This study analyzes the spatial distribution of young ultraviolet stars in the Small Magellanic Cloud, revealing hierarchical structures shaped by turbulence, supporting the turbulent star formation model.

Contribution

It provides the first detailed clustering analysis of young stars in the SMC using UV data, linking their distribution to turbulence-driven hierarchical star formation.

Findings

Identified 236 young stellar structures with sizes from a few parsecs to hundreds of parsecs.

Found fractal dimensions indicating significant lumpiness and irregular morphology.

Surface density distribution follows a log-normal pattern, consistent with turbulent interstellar medium.

Abstract

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 onboard 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 Dp = 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.