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PreprintCC BY 4.0arXiv

The role of velocity dispersion in the Kennicutt-Schmidt relation

  • Chryssi Koukouraki
  • Konstantinos Tassis
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Abstract

The resolved Kennicutt-Schmidt (KS) relation is a power-law relation between the surface densities of the star formation rate (ΣSFR) and molecular gas (Σmol) in star-forming galaxies on kiloparsec scales. Despite its apparent simplicity, it exhibits substantial scatter, suggesting the influence of additional physical parameters beyond gas surface density. We investigate whether molecular gas velocity dispersion (Δv) acts as a hidden parameter in the resolved KS relation in nearby galaxies. We use spatially resolved measurements of ΣSFR, Σmol, and Δv from the ALMaQUEST, EDGE-CALIFA, and PHANGS-ALMA surveys and from observations of the single galaxy M51. We identify two groups of galaxies based on the direction of the Δv gradient with respect to the best-fit KS line: one in which the Δv gradient is completely aligned with the KS line (group A) and thus does not contribute to the scatter, and one in which it has a component perpendicular to the line (group B) and contributes to the scatter. For each group, we fit the KS relation and examine the dependence of the residuals (Res) of the fit on Δv. In group B, we find a weak but statistically significant correlation between Res and Δv, which is consistent across all surveys. A three-dimensional fit including Δv yields ΣSFR ∝ Σmol1.15 Δv−0.59. We conclude that there is a set of star-forming galaxies for which the velocity dispersion acts as a secondary parameter in the KS relation, with higher Δv corresponding to lower ΣSFR at fixed Σmol. We find no obvious correlation between membership in this set and the other properties examined.

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Cite

BibTeXRIS
BibTeX
@misc{koukouraki2026role,
  title = {{The role of velocity dispersion in the Kennicutt-Schmidt relation}},
  author = {Chryssi Koukouraki and Konstantinos Tassis},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.39940},
  eprint = {2609.39940},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.39940},
  note = {CC BY 4.0},
}
RIS
TY  - UNPB
TI  - The role of velocity dispersion in the Kennicutt-Schmidt relation
AU  - Chryssi Koukouraki
AU  - Konstantinos Tassis
PY  - 2026
DA  - 2026/09/30
PB  - arXiv
DO  - 10.48550/arxiv.2609.39940
UR  - https://arxiv.org/abs/2609.39940
AB  - The resolved Kennicutt-Schmidt (KS) relation is a power-law relation between the surface densities of the star formation rate (Σ_SFR) and molecular gas (Σ_mol) in star-forming galaxies on kiloparsec scales. Despite its apparent simplicity, it exhibits substantial scatter, suggesting the influence of additional physical parameters beyond gas surface density. We investigate whether molecular gas velocity dispersion (Δv) acts as a hidden parameter in the resolved KS relation in nearby galaxies. We use spatially resolved measurements of Σ_SFR, Σ_mol, and Δv from the ALMaQUEST, EDGE-CALIFA, and PHANGS-ALMA surveys and from observations of the single galaxy M51. We identify two groups of galaxies based on the direction of the Δv gradient with respect to the best-fit KS line: one in which the Δv gradient is completely aligned with the KS line (group A) and thus does not contribute to the scatter, and one in which it has a component perpendicular to the line (group B) and contributes to the scatter. For each group, we fit the KS relation and examine the dependence of the residuals (Res) of the fit on Δv. In group B, we find a weak but statistically significant correlation between Res and Δv, which is consistent across all surveys. A three-dimensional fit including Δv yields Σ_SFR ∝ Σ_mol^1.15 Δv^−0.59. We conclude that there is a set of star-forming galaxies for which the velocity dispersion acts as a secondary parameter in the KS relation, with higher Δv corresponding to lower Σ_SFR at fixed Σ_mol. We find no obvious correlation between membership in this set and the other properties examined.
ER  -