Star Formation in Self-Gravitating Turbulent Fluids

Abstract

We present a model of star formation in self-gravitating turbulent gas. We treat the turbulent velocity $v_T$ as a dynamical variable, and assume that it is adiabatically heated by the collapse. The theory predicts the run of density, infall velocity, and turbulent velocity, and the rate of star formation in compact massive gas clouds. The turbulent pressure is dynamically important at all radii, a result of the adiabatic heating. The system evolves toward a coherent spatial structure with a fixed run of density, $\rho (r,t)\to \rho (r)$; mass flows through this structure onto the central star or star cluster. We define the sphere of influence of the accreted matter by $m_{\ast }=M_g(r_{\ast })$, where $m_{\ast }$ is the stellar plus disk mass in the nascent star cluster and $M_g(r)$ is the gas mass inside radius $r$. The density is given by a broken power law with a slope $-1.5$ inside $r_{\ast }$ and $\sim -1.6$ to $-1.8$ outside $r_{\ast }$. Both $v_T$ and the infall velocity $|u_r|$ decrease with decreasing $r$ for $r>r_{\ast }$; $v_T(r)\sim r^p$, the size-linewidth relation, with $p\approx 0.2-0.3$, explaining the observation that Larson's Law is altered in massive star forming regions. The infall velocity is generally smaller than the turbulent velocity at $r>r_{\ast }$. For $r<r_{\ast }$, the infall and turbulent velocities are again similar, and both increase with decreasing $r$ as $r^{-1/2}$, with a magnitude about half of the free-fall velocity. The accreted (stellar) mass grows super-linearly with time, ${\dot{M}}_{\ast }=\varphi M_{\mathrm{cl}}(t/{\tau }_{ff}{)}^2$, with $\varphi$ a dimensionless number somewhat less than unity, $M_{\mathrm{cl}}$ the clump mass and ${\tau }_{ff}$ the free-fall time of the clump. We suggest that small values of p can be used as a tracer of convergent collapsing flows.

17 pages, 8 figures, submitted to ApJ

References in corpus (5)

• Molecular Cloud Evolution II. From cloud formation to the early stages of star formation in decaying conditions
• On the Density Distribution in Star-forming Interstellar Clouds
• Class 0 Protostars in the Perseus Molecular Cloud: A Correlation Between the Youngest Protostars and the Dense Gas Distribution
• Time Varying Dynamical Star Formation Rate
• Outflow and Infall in a Sample of Massive Star Forming Regions II: Large Scale Kinematics

Cited by in corpus (26)

• Observational Evidence of Dynamic Star Formation Rate in Milky Way Giant Molecular Clouds
• Star cluster formation in cosmological simulations. I. Properties of young clusters
• The Physics of Star Cluster Formation and Evolution
• The statistical properties of stars and their dependence on metallicity
• Impact of Protostellar Outflows on Turbulence and Star Formation Efficiency in Magnetized Dense Cores
• Disruption of giant molecular clouds and formation of bound star clusters under the influence of momentum stellar feedback
• Moving mesh simulations of star forming cores in magneto-gravo-turbulence
• From diffuse gas to dense molecular cloud cores
• The Formation of Stellar Clusters in Magnetized, Filamentary Infrared Dark Clouds
• Turbulence in a self-gravitating molecular cloud core
• The density structure of supersonic self-gravitating turbulence
• Stellar mass spectrum within massive collapsing clumps III. Effects of temperature and magnetic field
• The Effects of Protostellar Jet Feedback on Turbulent Collapse
• Criteria for gravitational instability and quasi-isolated gravitational collapse in turbulent medium
• The evolution of temperature and density structures of OB cluster-forming molecular clumps
• Kinematics of Extremely Metal-poor Galaxies: Evidence for Stellar Feedback
• The Accelerating Pace of Star Formation
• A global view on star formation: The GLOSTAR Galactic plane survey VIII. Formaldehyde absorption in Cygnus~X
• Mass-size scaling M~ r^1.67 of massive star-forming clumps -- evidences of turbulence-regulated gravitational collapse
• Probing the initial conditions of high-mass star formation. III. Fragmentation and triggered star formation
• Reconstructing three-dimensional densities from two-dimensional observations of molecular gas
• Playing with FIRE: A Galactic Feedback-Halting Experiment Challenges Star Formation Rate Theories
• Saturation level of turbulence in collapsing gas clouds
• Probing the Global Dust Properties and Cluster Formation Potential of the Giant Molecular Cloud G148.24+00.41
• Density Exponent Analysis: Gravity-driven steepening of the density profiles of star-forming regions
• Amplification and generation of turbulence during self-gravitating collapse