Star Formation Laws and Thresholds From Interstellar Medium Structure and Turbulence

Renaud, Florent; Kraljic, Katarina; Bournaud, F.

doi:10.1088/2041-8205/760/1/l16

Cited by 71 publications

(86 citation statements)

References 50 publications

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“…Saintonge et al 2012). The theoretical interpretation proposed here is self-consistent, because the dense gas excess in mergers compared to gas-rich disks justifies the use of different α CO conversion factors, and at the same time this dense gas excess is theoretically expected to change the location of SB mergers in the Schmidt-Kennicutt diagram by lowering their gas consumption timescale by about 1 dex at a fixed gas surface density (Renaud et al 2012).…”

Section: Comparison Of α Co To Various Parameters and Modelssupporting

confidence: 60%

Modeling CO emission from hydrodynamic simulations of nearby spirals, starbursting mergers, and high-redshift galaxies

Bournaud

Daddi

Weiß

et al. 2015

A&A

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We model the intensity of emission lines from the CO molecule, based on hydrodynamic simulations of spirals, mergers, and highredshift galaxies with very high resolutions (3 pc and 10 3 M ) and detailed models for the phase-space structure of the interstellar gas including shock heating, stellar feedback processes, and galactic winds. The simulations are analyzed with a large velocity gradient (LVG) model to compute the local emission in various molecular lines in each resolution element, radiation transfer, opacity effect, and the intensity emerging from galaxies to generate synthetic spectra for various transitions of the CO molecule. This model reproduces the known properties of CO spectra and CO-to-H 2 conversion factors in nearby spirals and starbursting major mergers. The high excitation of CO lines in mergers is dominated by an excess of high-density gas, and the high turbulent velocities and compression that create this dense gas excess result in broad linewidths and low CO intensity-to-H 2 mass ratios. When applied to high-redshift gas-rich disks galaxies, the same model predicts that their CO-to-H 2 conversion factor is almost as high as in nearby spirals, and much higher than in starbursting mergers. High-redshift disk galaxies contain giant star-forming clumps that host a high-excitation component associated to gas warmed by the spatially concentrated stellar feedback sources, although CO(1−0) to CO(3−2) emission is dominated overall by low-excitation gas around the densest clumps. These results generally highlight a strong dependence of CO excitation and the CO-to-H 2 conversion factor on galaxy type, even at similar star formation rates or densities. The underlying processes are driven by the interstellar medium structure and turbulence and its response to stellar feedback, which depend on global galaxy structure and in turn affect the CO emission properties.

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Section: Comparison Of α Co To Various Parameters and Modelssupporting

confidence: 60%

Modeling CO emission from hydrodynamic simulations of nearby spirals, starbursting mergers, and high-redshift galaxies

Bournaud

Daddi

Weiß

et al. 2015

A&A

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“…Numerical simulations by Kraljic et al (2014) suggest that the change in slope of the Schmidt-Kennicutt relation between gas surface density and SFR from the low gas density regime to high gas density regime is the result of a transition from subsonic to supersonic turbulence (see also Renaud et al 2012). This transition may also be coupled to the transition from inefficient to efficient star formation.…”

Section: Introductionmentioning

confidence: 97%

The Nature of Turbulence in the LITTLE THINGS Dwarf Irregular Galaxies

Maier

Elmegreen

Hunter

et al. 2017

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We present probability density functions and higher order (skewness and kurtosis) analyses of the galaxy-wide and spatially-resolved H i column density distributions in the LITTLE THINGS sample of dwarf irregular galaxies. This analysis follows that of Burkhart et al. (2010) for the Small Magellanic Cloud. About 60% of our sample have galaxy-wide values of kurtosis that are similar to that found for the Small Magellanic Cloud, with a range up to much higher values, and kurtosis increases with integrated star formation rate. Kurtosis and skewness were calculated for radial annuli and for a grid of 32 pixel × 32 pixel kernels across each galaxy. For most galaxies, kurtosis correlates with skewness. For about half of the galaxies, there is a trend of increasing kurtosis with radius. The range of kurtosis and skewness values is modeled by small variations in the Mach number close to the sonic limit and by conversion of H i to molecules at high column density. The maximum H i column densities decrease with increasing radius in a way that suggests molecules are forming in the weak field limit, where H 2 formation balances photodissociation in optically thin gas at the edges of clouds.

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“…A number of useful global star formation frameworks and models have been developed over the last three decades (e.g., Wyse & Silk 1989;Silk 1997;Tan 2000;Elmegreen 2002;Krumholz & McKee 2005;Li et al 2005;Krumholz & Thompson 2007;Saitoh et al 2008;Krumholz et al 2009b;Silk & Norman 2009;Ostriker et al 2010;Ostriker & Shetty 2011;Renaud et al 2012;Faucher-Giguère et al 2013;Federrath 2013;Elmegreen 2015;Salim et al 2015). Many of these models consider the physical processes shaping the form of the KSR while treating its normalization as a flexible constant.…”

Section: Introductionmentioning

confidence: 99%

The Physical Origin of Long Gas Depletion Times in Galaxies

Semenov

Kravtsov

Gnedin

2017

ApJ

126

106

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We present a model that explains why galaxies form stars on a time scale significantly longer than the time scales of processes governing the evolution of interstellar gas. We show that gas evolves from a nonstar-forming to a star-forming state on a relatively short time scale and thus the rate of this evolution does not limit the star formation rate. Instead, the star formation rate is limited because only a small fraction of star-forming gas is converted into stars before star-forming regions are dispersed by feedback and dynamical processes. Thus, gas cycles into and out of star-forming state multiple times, which results in a long time scale on which galaxies convert gas into stars. Our model does not rely on the assumption of equilibrium and can be used to interpret trends of depletion times with the properties of observed galaxies and the parameters of star formation and feedback recipes in simulations. In particular, the model explains how feedback selfregulates the star formation rate in simulations and makes it insensitive to the local star formation efficiency. We illustrate our model using the results of an isolated L * -sized galaxy simulation that reproduces the observed Kennicutt-Schmidt relation for both molecular and atomic gas. Interestingly, the relation for molecular gas is almost linear on kiloparsec scales, although a nonlinear relation is adopted in simulation cells. We discuss how a linear relation emerges from non-self-similar scaling of the gas density PDF with the average gas surface density.

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Star Formation Laws and Thresholds From Interstellar Medium Structure and Turbulence

Cited by 71 publications

References 50 publications

Modeling CO emission from hydrodynamic simulations of nearby spirals, starbursting mergers, and high-redshift galaxies

Modeling CO emission from hydrodynamic simulations of nearby spirals, starbursting mergers, and high-redshift galaxies

The Nature of Turbulence in the LITTLE THINGS Dwarf Irregular Galaxies

The Physical Origin of Long Gas Depletion Times in Galaxies

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