Gravity-driven Emergence of Multi-fractal Density Structure in the Orion A Integral Shaped Filament
Abstract
Molecular clouds are often described as self-similar structures, although spatially averaged measures do not retain local variations in density scaling. We use the density exponent κρ (ρ∝ rκρ) to characterize the density structure of the Integral Shaped Filament (ISF) in Orion\,A. Applying the Multiscale Decomposition Reconstruction method to the Herschel column-density map, we find distinct density--scale relations across the connected filament. Their slopes steepen from κρ≈ −1.7 to −1.9 in the quiescent OMC-4/5 regions, through ≈ −2.1 in the star-forming OMC-2/3, to ≈ −2.3 in OMC-1, which hosts massive star formation. The ISF therefore does not follow a single local density-scaling exponent but exhibits multi-fractal density scaling. The pixel-level distributions show the same progression toward higher volume density and more negative κρ. Since κρ measures the concentration of gas toward smaller scales, we interpret this sequence as gravity-driven differential collapse: denser regions have shorter free-fall times and develop steeper density profiles. Longitudinal gas motions toward OMC-1 may limit the mass supply available for large-scale growth in the outer sub-regions and help maintain the observed range of local exponents. These results link local density scaling to gravitational concentration within a single connected filamentary system.
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BibTeX
@misc{zhao2026gravitydriven,
title = {{Gravity-driven Emergence of Multi-fractal Density Structure in the Orion A Integral Shaped Filament}},
author = {Mengke Zhao and Guang-Xing Li and Keping Qiu and Guangya Zeng},
howpublished = {arXiv},
year = {2026},
month = sep,
doi = {10.48550/arxiv.2609.24319},
eprint = {2609.24319},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2609.24319},
}
RIS
TY - UNPB
TI - Gravity-driven Emergence of Multi-fractal Density Structure in the Orion A Integral Shaped Filament
AU - Mengke Zhao
AU - Guang-Xing Li
AU - Keping Qiu
AU - Guangya Zeng
PY - 2026
DA - 2026/09/21
PB - arXiv
DO - 10.48550/arxiv.2609.24319
UR - https://arxiv.org/abs/2609.24319
AB - Molecular clouds are often described as self-similar structures, although spatially averaged measures do not retain local variations in density scaling. We use the density exponent κ_ρ (ρ∝ r^κ_ρ) to characterize the density structure of the Integral Shaped Filament (ISF) in Orion\,A. Applying the Multiscale Decomposition Reconstruction method to the Herschel column-density map, we find distinct density--scale relations across the connected filament. Their slopes steepen from κ_ρ≈ −1.7 to −1.9 in the quiescent OMC-4/5 regions, through ≈ −2.1 in the star-forming OMC-2/3, to ≈ −2.3 in OMC-1, which hosts massive star formation. The ISF therefore does not follow a single local density-scaling exponent but exhibits multi-fractal density scaling. The pixel-level distributions show the same progression toward higher volume density and more negative κ_ρ. Since κ_ρ measures the concentration of gas toward smaller scales, we interpret this sequence as gravity-driven differential collapse: denser regions have shorter free-fall times and develop steeper density profiles. Longitudinal gas motions toward OMC-1 may limit the mass supply available for large-scale growth in the outer sub-regions and help maintain the observed range of local exponents. These results link local density scaling to gravitational concentration within a single connected filamentary system.
ER -