A General Theory of Turbulence-regulated Star Formation, from Spirals to Ultraluminous Infrared Galaxies

By Mark R. Krumholz, C. McKee. 2005

783 citations recorded by the source corpus.

We derive an analytic prediction for the star formation rate in environments ranging from normal galactic disks to starbursts and ULIRGs in terms of the observables of those systems. Our calculation is based on three premises: (1) star formation occurs in virialized molecular clouds that are supersonically turbulent; (2) the density distribution within these clouds is lognormal, as expected for supersonic isothermal turbulence; and (3) stars form in any subregion of a cloud that is so overdense that its gravitational potential energy exceeds the energy in turbulent motions. We show that a theory based on this model is consistent with simulations and with the observed star formation rate in the Milky Way. We use our theory to derive the Kennicutt-Schmidt law from first principles and make other predictions that can be tested by future observations. We also provide an algorithm for estimating the star formation rate that is suitable for inclusion in numerical simulations.

Subfields: Astronomy and Astrophysics

View Paper: https://www.semanticscholar.org/paper/5617736fc088fb3cfea5adb936cd0b87c8305403

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In Astronomy and Astrophysics

1. P. Hopkins
2. Mark R. Krumholz
3. L. Hernquist
4. E. Quataert
5. R. Somerville
6. Ralf Klessen
7. R. Dav'e
8. A. Dekel

Citations in the corpus

• The first galaxies : assembly, cooling and the onset of turbulence (2008, background): “…4), length scale and strength of the turbulence are the most important parameters governing its fragmentation behaviour and consequently the properties of star formation, such as its timescale and overall ef- ficiency (Klessen et al. 2000; Vázquez-Semadeni et al. 2003; Krumholz & McKee 2005).”
• THE SCALE DEPENDENCE OF THE MOLECULAR GAS DEPLETION TIME IN M33 (2010, background): “Krumholz & McKee (2005); Krumholz & Tan (2007) suggested that the cloud free-fall time determines τdep to first order, but based on Rosolowsky et al. (2003), the dynamic range in free-fall times for M33 clouds is low.”
• RADIATION-HYDRODYNAMIC SIMULATIONS OF THE FORMATION OF ORION-LIKE STAR CLUSTERS. II. THE INITIAL MASS FUNCTION FROM WINDS, TURBULENCE, AND RADIATION (2012, background): “Observationally, the dimensionless star formation rate (Krumholz & McKee 2005) ff ≡ Ṁ∗ (1/2)Mc/tff , (10) where the factor of 1/2 arises because half the cloud mass is above the density 〈ρ〉M used to define tff , is ∼ 1%, with roughly half a dex scatter, over a very wide range of densities and…”
• Kinematics in Young Star Clusters and Associations with Gaia DR2 (2018, background): “…kinematics in molecular clouds, which may include effects of supersonic turbulence (Larson 1981; Mac Low & Klessen 2004; Padoan & Nordlund 2002; Krumholz & McKee 2005), free-fall velocities of collapsing clouds (VázquezSemadeni et al. 2017), and/or accretion of material onto molecular clouds…”
• A general model for the CO–H2 conversion factor in galaxies with applications to the star formation law (2011, background): “Both observations and theory have suggested that the star formation efficiency per free-fall time ff in molecular gas is approximately constant (Krumholz & McKee 2005; Krumholz & Tan 2007; Evans et al. 2009; Ostriker & Shetty 2011; Krumholz, Dekel & McKee 2012).”
• Globular clusters as the relics of regular star formation in ‘normal’ high-redshift galaxies (2015, background): “15star (cf. Krumholz & McKee 2005).”
• Variations in the Galactic star formation rate and density thresholds for star formation (2012, background): “Theorists have wrestled with this before (e.g. Krumholz & McKee 2005; Padoan & Nordlund 2011; Krumholz et al. 2012) and we are currently seeking to test these scenarios.”
• Dusty Star Forming Galaxies at High Redshift (2014, background): “Future surveys of HCN (J = 1–0) fromhigh-z SMGs, and comparisons to low-z relationswill provide valuable insight into the physical conditions that govern star formation (e.g. Krumholz and McKee, 2005; Andrews and Thompson, 2011; Hopkins et al., 2013e).”
• Forming disc galaxies in ΛCDM simulations (2006, background): “…at which SF and feedback happen (a few pc) makes it necessary to develop simplified models to describe SF and subsequent energy feedback from supernovae (SNe) at galactic scales (0.1–1 kpc; Efstathiou 2000; Silk 2001; Wada & Norman 2001; Ferrara 2002; Krumholz & McKee 2005; Slyz et al. 2005).”
• PHIBSS: Unified Scaling Relations of Gas Depletion Time and Molecular Gas Fractions (2017, background): “An important open issue is whether the depletion time for converting molecular gas to stars on galactic scales is set locally within clouds (Krumholz & McKee 2005) or on large galactic scales (Elmegreen 1997, Silk 1997).”
• The structure of the interstellar medium of star‐forming galaxies (2011, background): “One interpretation is that the instantaneous star formation efficiency of ∼1 per cent per dynamical time can be explained as a consequence of the statistics of the lognormal turbulent density field (Nordlund & Padoan 1999; Vázquez-Semadeni et al. 2003; Li et al. 2004; Krumholz & McKee 2005).”
• THE ROLE OF STELLAR FEEDBACK IN THE FORMATION OF GALAXIES (2007, result): “This is roughly consistent with estimations of the star formation efficiency in molecular clouds (Zuckerman & Evans 1974; Krumholz & McKee 2005; Krumholz & Tan 2007).”
• Feedback-regulated star formation and escape of LyC photons from mini-haloes during reionization (2016, background): “An important quantity in Equation 2 is the critical density (scrit), which may be regarded as the minimum density above which gas in the post-shock regions of a cloud is magnetically supercritical and thus can collapse (Krumholz & McKee 2005; Padoan & Nordlund 2011; Hennebelle & Chabrier 2011).”
• THE STAR FORMATION RATE OF TURBULENT MAGNETIZED CLOUDS: COMPARING THEORY, SIMULATIONS, AND OBSERVATIONS (2012, methodology): “We follow the standard terminology and use the Star Formation Rate per Freefall Time (SFRff), as coined by Krumholz & McKee (2005), which is the mass fraction going into stars per time, where the time is expressed in units of the mean freefall time.”
• A comparison between grid and particle methods on the statistics of driven, supersonic, isothermal turbulence (2010, background): “…therein); the few per- cent efficiency with which gas is converted into stars (Padoan 1995; Vázquez-Semadeni, Ballesteros-Paredes & Klessen 2003; Krumholz & McKee 2005; Elmegreen 2008); most likely determines in large part the mass distribution of star forming cores (the core mass…”
• A study of the gas–star formation relation over cosmic time (2010, background): “5gas since τff ∝ ρ−1/2gas , (2) where the (dimensionless) star formation efficiency εff = τff/τd is the fraction of the available gas mass converted to stars in a freefall time (e.g. Krumholz & McKee 2005).”
• THE SPITZER c2d LEGACY RESULTS: STAR-FORMATION RATES AND EFFICIENCIES; EVOLUTION AND LIFETIMES (2008, background): “Krumholz & McKee (2005) define the star formation rate per unit free fall time (SFRff ) to be the fraction of an object’s mass that turns into stars in a free fall time at the object’s mean density.”
• IONIZING PHOTON ESCAPE FRACTIONS FROM HIGH-REDSHIFT DWARF GALAXIES (2008, background): “Our choice of the star formation efficiency is in agreement with Krumholz & McKee (2005), who find that this fraction in a free-fall time is 0.077α−0.68vir M −0.32, where αvir is a virialization parameter and is near unity, and M is the turbulent Mach number.”
• How Stellar Feedback Simultaneously Regulates Star Formation and Drives Outflows (2015, background): “As noted byTK14, virtually all previous models for how momentum deposition drives turbulence (e.g.Krumholz & McKee 2005; Krumholz et al. 2009b; Murray et al. 2010; Ostriker & Shetty 2011; FQH13) and generates outflows (e.g.Murray et al. 2005, 2011; Thompson et al. 2005) have considered only the…”
• Why are most molecular clouds not gravitationally bound (2011, background): “This could be magnetic fields and slow ambipolar diffusion (Shu et al. 1987; Basu & Mouschovias 1994; Allen & Shu 2000; Mouschovias et al. 2006; Shu et al. 2007), or microturbulence (Krumholz & McKee 2005; Krumholz et al. 2006).”