Evolution of fractality in centrally concentrated young clusters

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Main Authors: Akhmetali, Almat, Assilkhan, Adilkhan, Mac Low, Mordecai-Mark, Ussipov, Nurzhan, Zaidyn, Marat, Abdikamalov, Ernazar, Sills, Alison, Pang, Xiaoying, Shukirgaliyev, Bekdaulet
Format: Preprint
Published: 2026
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author Akhmetali, Almat
Assilkhan, Adilkhan
Mac Low, Mordecai-Mark
Ussipov, Nurzhan
Zaidyn, Marat
Abdikamalov, Ernazar
Sills, Alison
Pang, Xiaoying
Shukirgaliyev, Bekdaulet
author_facet Akhmetali, Almat
Assilkhan, Adilkhan
Mac Low, Mordecai-Mark
Ussipov, Nurzhan
Zaidyn, Marat
Abdikamalov, Ernazar
Sills, Alison
Pang, Xiaoying
Shukirgaliyev, Bekdaulet
contents We investigate the structural evolution of young star clusters forming within centrally concentrated molecular clouds. Our simulations use the Torch framework, which integrates the FLASH magnetohydrodynamics code with the AMUSE environment, enabling a self-consistent treatment of gas dynamics, star formation, stellar evolution, radiative transfer, and gravitational interactions. We quantify cluster structure using the $Q$ parameter for fractality and compute fractal dimensions via two methods: box-counting and correlation dimension. Our results show that clusters generally inherit fractal substructure from their parental clouds, which is typically erased within $\sim 2.5\,t_\mathrm{ff}$ through dynamical relaxation. Massive stars can induce the formation of secondary subclusters via feedback, with outcomes strongly dependent on stellar mass and formation timing. Interactions among subclusters, including mergers and dispersal, can extend fractal structure beyond $4\,t_\mathrm{ff}$. We also find systematic correlations between the fractality parameter $Q$ and the fractal dimension: fractality is positively correlated with both the correlation and box-counting dimensions, with the correlation dimension exhibiting a stronger correlation. These results demonstrate how stellar feedback and internal dynamics jointly shape the measurable fractal properties of embedded star clusters.
format Preprint
id arxiv_https___arxiv_org_abs_2603_16183
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Evolution of fractality in centrally concentrated young clusters
Akhmetali, Almat
Assilkhan, Adilkhan
Mac Low, Mordecai-Mark
Ussipov, Nurzhan
Zaidyn, Marat
Abdikamalov, Ernazar
Sills, Alison
Pang, Xiaoying
Shukirgaliyev, Bekdaulet
Astrophysics of Galaxies
We investigate the structural evolution of young star clusters forming within centrally concentrated molecular clouds. Our simulations use the Torch framework, which integrates the FLASH magnetohydrodynamics code with the AMUSE environment, enabling a self-consistent treatment of gas dynamics, star formation, stellar evolution, radiative transfer, and gravitational interactions. We quantify cluster structure using the $Q$ parameter for fractality and compute fractal dimensions via two methods: box-counting and correlation dimension. Our results show that clusters generally inherit fractal substructure from their parental clouds, which is typically erased within $\sim 2.5\,t_\mathrm{ff}$ through dynamical relaxation. Massive stars can induce the formation of secondary subclusters via feedback, with outcomes strongly dependent on stellar mass and formation timing. Interactions among subclusters, including mergers and dispersal, can extend fractal structure beyond $4\,t_\mathrm{ff}$. We also find systematic correlations between the fractality parameter $Q$ and the fractal dimension: fractality is positively correlated with both the correlation and box-counting dimensions, with the correlation dimension exhibiting a stronger correlation. These results demonstrate how stellar feedback and internal dynamics jointly shape the measurable fractal properties of embedded star clusters.
title Evolution of fractality in centrally concentrated young clusters
topic Astrophysics of Galaxies
url https://arxiv.org/abs/2603.16183