The Formation of Stellar Clusters in Turbulent Molecular Clouds: Effects of the Equation of State

By Yue-xing Li, Ralf Klessen, M. Mac Low. 2002

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We study the effect of varying the equation of state on the formation of stellar clusters in turbulent molecular clouds using three-dimensional, smoothed particle hydrodynamics simulations. Our results show that the equation of state helps determine how strongly self-gravitating gas fragments. The degree of fragmentation decreases with increasing polytropic exponent γ in the range 0.2 < γ < 1.4, although the total amount of mass accreted onto collapsed fragments appears to remain roughly constant through that range. Low values of γ are expected to lead to the formation of dense clusters of low-mass stars, while γ > 1 probably results in the formation of isolated and massive stars. Fragmentation and collapse ceases entirely for γ > 1.4, as expected from analytic arguments. The mass spectrum of overdense gas clumps is roughly lognormal for non-self-gravitating turbulent gas, but changes to a power law under the action of gravity. The spectrum of collapsed cores, on the other hand, remains lognormal for γ ≤ 1 but flattens markedly for γ > 1. The density probability function approaches lognormal, with widths that decrease with increasing γ. Primordial gas may have effective γ > 1, in which case these results could help explain why models of the formation of the first stars tend to produce isolated, massive objects.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/c42618b9bb1e3459e4765222818e876172b80df0

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Citations in the corpus

Comparing the statistics of interstellar turbulence in simulations and observations - Solenoidal versus compressive turbulence forcing (2009, background): “…et al. 1997; Stone et al. 1998; Mac Low et al. 1998; Mac Low 1999; Klessen et al. 2000; Heitsch et al. 2001; Klessen 2001; Boldyrev et al. 2002; Li et al. 2003; Padoan et al. 2004; Jappsen et al. 2005; Ballesteros-Paredes et al. 2006; Kritsuk et al. 2007; Dib et al. 2008; Kissmann et al. 2008;…”
The stellar and sub-stellar IMF of simple and composite populations (2011, background): “Such events of isolated massive-star formation are conceivable if the equation of state of the inter-stellar medium can become stiff (Li et al. 2003).”
THE STAR FORMATION RATE OF TURBULENT MAGNETIZED CLOUDS: COMPARING THEORY, SIMULATIONS, AND OBSERVATIONS (2012, background): “In the case of B ∝ ρ0, i.e., for no density correlation of the magnetic field, Equation (4) reduces to the well-known and frequently used hydrodynamic (HD) expression, σ2s = ln ( 1 + b2M2 ) with β →∞ (e.g., Padoan et al. 1997; Passot & Vázquez-Semadeni 1998; Ostriker et al. 2001; Lemaster & Stone 2”
Can Supermassive Black Holes Form in Metal-enriched High-Redshift Protogalaxies? (2008, background): “Roughly speaking, fragmentation occurs efficiently when the effective adiabatic index @ ln p/@ ln P1, i.e., during the temperature drops, and almost stops when isothermality breaks ( k 1) as also shown by the simulations of Li et al. (2003).”
The Density Probability Distribution in Compressible Isothermal Turbulence: Solenoidal versus Compressive Forcing (2008, methodology): “…and resolutions, typically smaller but roughly consistent values of b are found compared to b ∼ 1 by PV98, e.g., b ∼ 0.35 using 200, 000 SPH particles (Li et al. 2003), b ∼ 0.26 using ENZO with 10243 cells (Kritsuk et al. 2007)4, b∼ 0.37 using another gridbased method with 5123 cells (Beetz et…”
Thermal physics, cloud geometry and the stellar initial mass function (2005, methodology): “The work of Li et al. (2003) shows that the amount of fragmentation that occurs is indeed very sensitive to the assumed temperature– density relation.”
The Stellar Mass Spectrum from Non-Isothermal Gravoturbulent Fragmentation (2004, methodology): “In their numerical study Li et al. (2003) found, for a range of assumed polytropic equations of state, that the amount of fragmentation that occurs is indeed very sensitive to the value of the polytropic exponentγ, especially for values ofγ near unity (see also, Arcoragi et al. 1991).”
Physical Processes in the Interstellar Medium (2014, background): “Depending on the polytropic exponent γ in the equation of state (215), the PDF develops a power-law tail at low densities for γ > 1 and at high densities for γ 1 (see e.g. Li et al., 2003).”
Turbulent Structure of a Stratified Supernova-driven Interstellar Medium (2005, background): “In contrast, several numerical experiments that included either self-gravity of gas or non-isothermal equation of state (γ 6= 1) reported that high-density tails develop in nonisothermal cases (Scalo et al. 1998; Li et al. 2003).”
Interstellar Turbulence I: Observations and Processes (2004, methodology): “…that the pdf should exhibit an approximately lognormal distribution if the gas is isothermal (Ostriker, Gammie & Stone 1999; Klessen 2000; Ostriker et al. 2001; Li et al. 2003), with quasi-power-law tails if nonisothermal (Passot & Vázquez-Semadeni 1998; Scalo et al. 1998; Nordlund & Padoan 1999).”
THE INTERSTELLAR MEDIUM IN DISTANT STAR-FORMING GALAXIES: TURBULENT PRESSURE, FRAGMENTATION, AND CLOUD SCALING RELATIONS IN A DENSE GAS DISK AT z = 2.3 (2011, background): “…gas may play a crucial role in defining the thermodynamic state of the dense gas and hence on the stellar IMF and its mass scale (i.e. the IMF “knee”; Li et al. 2003; Jappsen et al. 2005; Bonnell et al. 2006)8 The very strong turbulence present in the ISM of galaxies such as SMMJ2135 (as well as…”
THE FRACTAL DENSITY STRUCTURE IN SUPERSONIC ISOTHERMAL TURBULENCE: SOLENOIDAL VERSUS COMPRESSIVE ENERGY INJECTION (2007, background): “…1994; Padoan et al. 1997; Passot & Vázquez-Semadeni 1998; Stone et al. 1998; Mac Low 1999; Klessen 2000; Ostriker et al. 2001; Boldyrev et al. 2002; Li et al. 2003; Padoan et al. 2004b; Jappsen et al. 2005; Ballesteros-Paredes et al. 2006; Kritsuk et al. 2007; Lemaster & Stone 2008).”
The density variance–Mach number relation in supersonic turbulence – I. Isothermal, magnetized gas (2012, background): “However, depending on whether the equation of state is softer or harder than isothermal, it might acquire power-law tails at either high or low densities (Passot & Vázquez-Semadeni 1998; Scalo et al. 1998; Wada 2001; Li et al. 2003; McKee & Ostriker 2007).”
Relativistic jet feedback – III. Feedback on gas discs (2018, background): “The gas more prone to ablation below the critical density of ∼ 100 − 300 cm−3 is 7 See Li et al. (2003) for a discussion on mass vs volume weighted PDFs. MNRAS 000, ??”