A Momentum-Regulated Model For Star Formation Efficiency in Giant Molecular Clouds
Abstract
We present a minimal analytic framework to investigate the star formation efficiency per free-fall time, εff, in giant molecular clouds (GMCs), focusing on the origin of the observed clustering around εff ∼ 0.01. We model the time evolution of the turbulent velocity dispersion through a momentum balance between stellar feedback and turbulent dissipation, and show that this generically leads to a stable low-efficiency equilibrium with only weak dependence on global cloud properties. We extend the framework by including a phenomenological contribution from gravity-driven turbulence and find that both feedback- and gravity-driven motions converge to similar equilibrium states under typical GMC conditions. The efficiency can be expressed as the ratio between a gravitational velocity scale and an effective feedback velocity scale, providing a physically transparent interpretation of self-regulated star formation. The model provides a simple, physically motivated interpretation of observed gas-star formation scaling relations, including a Schmidt-like scaling at cloud scales and a Kennicutt-like scaling when averaged over cloud populations. Comparison with observed GMC properties shows agreement within a factor of a few and highlights the weak sensitivity of εff to cloud parameters. Despite its simplicity, the framework captures the leading-order interplay between turbulence, gravity, and feedback, and provides a physically transparent explanation for the origin and robustness of low star formation efficiencies in GMCs.
Versions
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BibTeX
@misc{bertram2026momentumregulated,
title = {{A Momentum-Regulated Model For Star Formation Efficiency in Giant Molecular Clouds}},
author = {Erik Bertram},
howpublished = {arXiv},
year = {2026},
month = jul,
doi = {10.48550/arxiv.2607.06727},
eprint = {2607.06727},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2607.06727},
}
RIS
TY - UNPB
TI - A Momentum-Regulated Model For Star Formation Efficiency in Giant Molecular Clouds
AU - Erik Bertram
PY - 2026
DA - 2026/07/07
PB - arXiv
DO - 10.48550/arxiv.2607.06727
UR - https://arxiv.org/abs/2607.06727
AB - We present a minimal analytic framework to investigate the star formation efficiency per free-fall time, ε_ff, in giant molecular clouds (GMCs), focusing on the origin of the observed clustering around ε_ff ∼ 0.01. We model the time evolution of the turbulent velocity dispersion through a momentum balance between stellar feedback and turbulent dissipation, and show that this generically leads to a stable low-efficiency equilibrium with only weak dependence on global cloud properties. We extend the framework by including a phenomenological contribution from gravity-driven turbulence and find that both feedback- and gravity-driven motions converge to similar equilibrium states under typical GMC conditions. The efficiency can be expressed as the ratio between a gravitational velocity scale and an effective feedback velocity scale, providing a physically transparent interpretation of self-regulated star formation. The model provides a simple, physically motivated interpretation of observed gas-star formation scaling relations, including a Schmidt-like scaling at cloud scales and a Kennicutt-like scaling when averaged over cloud populations. Comparison with observed GMC properties shows agreement within a factor of a few and highlights the weak sensitivity of ε_ff to cloud parameters. Despite its simplicity, the framework captures the leading-order interplay between turbulence, gravity, and feedback, and provides a physically transparent explanation for the origin and robustness of low star formation efficiencies in GMCs.
ER -