Hierarchical star formation in nearby galaxies

TL;DR

This study investigates the hierarchical spatial distribution of young stars in three nearby galaxies, revealing fractal structures and turbulence-regulated star formation processes across different scales.

Contribution

It provides a detailed analysis of young stellar group properties and their hierarchical organization in multiple galaxies, extending previous work to larger scales.

Findings

Identified 573 young stellar groups in NGC 2403.

Found hierarchical clustering with fractal dimensions ~1.5-1.6.

Star formation appears regulated by supersonic turbulence.

Abstract

Aims: The purpose of this work is to study the properties of the spatial distribution of the young population in three nearby galaxies in order to better understand the first stages of star formation. Methods: We used ACS/HST photometry and the "path-linkage criterion" in order to obtain a catalog of young stellar groups (YSGs) in the galaxy NGC 2403. We studied the internal distribution of stars in these YSGs using the Q parameter. We extended these analyses to the YSGs detected in in NGC 300 and NGC 253 our previous works. We built the young stars' density maps for these three galaxies. Through these maps, we were able to identify and study young stellar structures on larger scales. Results: We found 573 YSGs in the galaxy NGC 2403, for which we derived their individual sizes, densities, luminosity function,and other fundamental characteristics. We find that the vast majority of the YSGs in NGC 2403, NGC 300 and NGC 253 present inner clumpings, following the same hierarchical behavior that we observed in the young stellar structures on larger scales in these galaxies. We derived values of the fractal dimension for these structures between ~ 1.5 and 1.6. These values are very similar to those obtained in other star forming galaxies and in the interstellar medium, suggesting that the star formation process is regulated by supersonic turbulence.