Virial-based extraction of structures in numerical simulations: The vibes tool
Abstract
Context . The processes that determine the stellar initial mass function (IMF) and its connection to the core mass function (CMF) are among the major open questions in star formation. The definition of a core remains unclear, yet the way they are extracted from simulations and observations critically shapes the CMF. Nowadays, cores are mostly detected through their density or intensity only. Aims . We aim to explore a new way to define cores in 3D numerical simulations based on a direct application of the virial theorem, and break free from some limitations induced by density-based methods. We intend to improve the accuracy and the physical meaning of the extracted cores. Methods . We developed vibes , an innovative method that makes full use of the virial theorem to extract overdensities in simulation snapshots. It works by building structures iteratively around density peaks, and applying the virial theorem to the structure at each iteration. Then, the structure boundary is set from the evolution of the its energy as it spatially grows. Results . We used STARFORGE simulations to test the sensitivity of the extraction process to the main working parameters (constraints on the structure shape, iteration step, and peak selection criteria). This sensitivity is observed to be low. We compared our extraction with two density-based extraction algorithms, hop and dendrogram , that are observed to be very sensitive to their input density threshold parameter. Vibes returns structures that are coherent to each other and physically motivated, and it appears much more stable than existing 3D extraction tools. Conclusions . We present vibes , a new structure extraction tool based on the virial equilibrium of the dense gas. By defining the boundary of the cores on a physical criterion rather than on a user-defined set of density parameters, we expect such extracted cores to be closer to their forsaken definition: gas reservoirs that will form a single star or a close multiple system. The tool also provides a way to probe the physics of dense structures by following the evolution of their virial energy as they spatially grow.
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BibTeX
@article{chevalier2026virialbased,
title = {{Virial-based extraction of structures in numerical simulations: The vibes tool}},
author = {S. Chevalier and F. Louvet and Y. Bernard and F. Motte and D.J. Price and N. Brucy and M. Valeille-Manet and M. González-Garcia and E. Moraux and I. Joncour and B. Thomasson and P. Didelon},
journal = {Advances in Archaeological Practice},
year = {2026},
month = nov,
doi = {10.1051/0004-6361/202659341},
eprint = {2606.08494},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05847876v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - Virial-based extraction of structures in numerical simulations: The vibes tool
AU - S. Chevalier
AU - F. Louvet
AU - Y. Bernard
AU - F. Motte
AU - D.J. Price
AU - N. Brucy
AU - M. Valeille-Manet
AU - M. González-Garcia
AU - E. Moraux
AU - I. Joncour
AU - B. Thomasson
AU - P. Didelon
PY - 2026
DA - 2026/11/02
JO - Advances in Archaeological Practice
DO - 10.1051/0004-6361/202659341
UR - https://hal.science/hal-05847876v1
AB - Context . The processes that determine the stellar initial mass function (IMF) and its connection to the core mass function (CMF) are among the major open questions in star formation. The definition of a core remains unclear, yet the way they are extracted from simulations and observations critically shapes the CMF. Nowadays, cores are mostly detected through their density or intensity only. Aims . We aim to explore a new way to define cores in 3D numerical simulations based on a direct application of the virial theorem, and break free from some limitations induced by density-based methods. We intend to improve the accuracy and the physical meaning of the extracted cores. Methods . We developed vibes , an innovative method that makes full use of the virial theorem to extract overdensities in simulation snapshots. It works by building structures iteratively around density peaks, and applying the virial theorem to the structure at each iteration. Then, the structure boundary is set from the evolution of the its energy as it spatially grows. Results . We used STARFORGE simulations to test the sensitivity of the extraction process to the main working parameters (constraints on the structure shape, iteration step, and peak selection criteria). This sensitivity is observed to be low. We compared our extraction with two density-based extraction algorithms, hop and dendrogram , that are observed to be very sensitive to their input density threshold parameter. Vibes returns structures that are coherent to each other and physically motivated, and it appears much more stable than existing 3D extraction tools. Conclusions . We present vibes , a new structure extraction tool based on the virial equilibrium of the dense gas. By defining the boundary of the cores on a physical criterion rather than on a user-defined set of density parameters, we expect such extracted cores to be closer to their forsaken definition: gas reservoirs that will form a single star or a close multiple system. The tool also provides a way to probe the physics of dense structures by following the evolution of their virial energy as they spatially grow.
SN - 2326-3768
ER -