Star formation laws and thresholds from ISM structure and turbulence

Abstract

We present an analytical model of the relation between the surface density of gas and star formation rate in galaxies and clouds, as a function of the presence of supersonic turbulence and the associated structure of the interstellar medium. The model predicts a power-law relation of index 3/2, flattened under the effects of stellar feedback at high densities or in very turbulent media, and a break at low surface densities when ISM turbulence becomes too weak to induce strong compression. This model explains the diversity of star formation laws and thresholds observed in nearby spirals and their resolved regions, the Small Magellanic Cloud, high-redshift disks and starbursting mergers, as well as Galactic molecular clouds. While other models have proposed interstellar dust content and molecule formation to be key ingredients to the observed variations of the star formation efficiency, we demonstrate instead that these variations can be explained by interstellar medium turbulence and structure in various types of galaxies.

6 pages, re-submitted to ApJL after referee report

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• Modelling CO emission from hydrodynamic simulations of nearby spirals, starbursting mergers, and high-redshift galaxies
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• Morphology and enhanced star formation in a Cartwheel-like ring galaxy
• The new semianalytic code GalICS 2.0 - Reproducing the galaxy stellar mass function and the Tully-Fisher relation simultaneously
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• Large-scale turbulent driving regulates star formation in high-redshift gas-rich galaxies
• From starburst to quenching: merger-driven evolution of the star formation regimes in a shell galaxy
• The Nature of Turbulence in the LITTLE THINGS Dwarf Irregular Galaxies
• Connecting the Cosmic Star Formation Rate with the Local Star Formation
• Physical Properties and Scaling Relations of Molecular Clouds: the Impact of Star Formation
• Turbulence and Star Formation in a Sample of Spiral Galaxies