The structure of the thermally bistable and turbulent atomic gas in the local interstellar medium

Abstract

This paper is a numerical study of the condensation of the warm neutral medium (WNM) into cold neutral medium (CNM) structures under the effect of turbulence and thermal instability. Using low resolution simulations we explored the impact of the WNM initial density and properties of the turbulence (stirring in Fourier with a varying mix of solenoidal and compressive modes) on the cold gas formation. Two sets of initial conditions which match the observations were selected to produce high resolution simulations (1024^3) allowing to study in details the properties of the produced dense structures. For typical values of the density, pressure and velocity dispersion of the WNM in the solar neighborhood, the turbulent motions of the HI can not provoque the phase transition from WNM to CNM, whatever their amplitude and their distribution in solenoidal and compressive modes. On the other hand we show that a quasi-isothermal increase in WNM density of a factor of 2 to 4 is enough to induce the phase transition, leading to the transition of about 40 percent of the gas to the cold phase within 1 Myr. Given the observed properties of the HI in the local ISM, the WNM and individual CNM structures in the local ISM are sub or transsonic and their dynamics are tightly interwoven. The velocity field bears the evidence of subsonic turbulence with a 2D power spectrum following the Kolmogorov law as P(k) \sim k^{-8/3} while the density is highly contrasted with a singificantly shallower power spectrum, reminiscent of what is observed in the cold ISM. Supra-thermal line width observed for CNM might be the result of relative velocity between cold structures. Finally, the cold structures denser than 5 cm^{-3} reproduce well the laws M \sim L^{2.25-2.28} and sigma(v) \sim 0.5-0.8L^{1/3} generally observed in molecular clouds.

21 pages, 24 figures

References in corpus (16)

• Theory of Star Formation
• The Statistics of Supersonic Isothermal Turbulence
• The Density Probability Distribution in Compressible Isothermal Turbulence: Solenoidal versus Compressive Forcing
• A High Order Godunov Scheme with Constrained Transport and Adaptive Mesh Refinement for Astrophysical MHD
• Numerical simulations of compressively driven interstellar turbulence: I. Isothermal gas
• From the warm magnetized atomic medium to molecular clouds
• The Fractal Density Structure in Supersonic Isothermal Turbulence: Solenoidal versus Compressive Energy Injection
• The Birth of Molecular Clouds: Formation of Atomic Precursors in Colliding Flows
• Dark matter in the Milky Way, II. the HI gas distribution as a tracer of the gravitational potential
• Dependence of Interstellar Turbulent Pressure on Supernova Rate
• Regulation of Star Formation Rates in Multiphase Galactic Disks: Numerical Tests of the Thermal/Dynamical Equilibrium Model
• Low-Mach-number turbulence in interstellar gas revealed by radio polarization gradients
• The Generation and Dissipation of Interstellar Turbulence - Results from Large Scale High Resolution Simulations
• Gaussian decomposition of HI surveys. III. Local HI
• Flux Correlations in Supersonic Isothermal Turbulence
• Physical properties of a very diffuse HI structure at high Galactic latitude

Cited by in corpus (55)

• Physical properties of molecular clouds for the entire Milky Way disk
• The SILCC (SImulating the LifeCycle of molecular Clouds) project: I. Chemical evolution of the supernova-driven ISM
• Modelling the supernova-driven ISM in different environments
• Survival and mass growth of cold gas in a turbulent, multiphase medium
• GHIGLS: HI mapping at intermediate Galactic latitude using the Green Bank Telescope
• Cold Milky Way Hi gas in filaments
• Thermal Phases of the Neutral Atomic Interstellar Medium -- from Solar Metallicity to Primordial Gas
• On the formation of density filaments in the turbulent interstellar medium
• Probing interstellar turbulence in cirrus with deep optical imaging: no sign of energy dissipation at 0.01 pc scale
• ROHSA: Regularized Optimization for Hyper-Spectral Analysis - Application to phase separation of 21 cm data
• Properties of cold and warm HI gas phases derived from a Gaussian decomposition of HI4PI data
• The Per-Tau Shell: A Giant Star-Forming Spherical Shell Revealed by 3D Dust Observations
• Histogram of oriented gradients: a technique for the study of molecular cloud formation
• Filament formation in wind-cloud interactions. II. Clouds with turbulent density, velocity, and magnetic fields
• The Survival of Multiphase Dusty Clouds in Hot Winds
• Pressure balance in the multiphase ISM of cosmologically simulated disk galaxies
• Physical properties and scaling relations of molecular clouds: the effect of stellar feedback
• Cosmic-ray propagation in the bi-stable interstellar medium. I. Conditions for cosmic-ray trapping
• Modelling and simulation of large-scale polarized dust emission over the southern Galactic cap using the GASS HI data
• 3D chemical structure of diffuse turbulent ISM. I. Statistics of the HI-to-H${}_2$ transition
• Filamentary flow and magnetic geometry in evolving cluster-forming molecular cloud clumps
• DHIGLS: DRAO H I Intermediate Galactic Latitude Survey
• Exploring the properties of warm and cold atomic hydrogen in the Taurus and Gemini regions
• Thermal and turbulent properties of the Warm Neutral Medium in the solar neighborhood
• Chemical Abundances in a Turbulent Medium -- H${}_2$, OH${}^{+}$, H${}_2$O${}^{+}$, ArH${}^{+}$
• Power-law tails in probability density functions of molecular cloud column density
• Recovering interstellar gas properties with HI spectral lines: A comparison between synthetic spectra and 21-SPONGE
• HI anisotropies associated with radio-polarimetric filaments. Steep power spectra associated with cold gas
• Anisotropies in the HI gas distribution toward 3C196
• Atomic Chemistry In Turbulent Astrophysical Media I: Effect of Atomic Cooling
• Structure formation in a colliding flow: The Herschel view of the Draco nebula
• Cooling driven coagulation
• The multiphase and magnetized neutral hydrogen seen by LOFAR
• Study Turbulence and Probe Magnetic Field Using Gradients Technique: Application to HI-to-H2 Transition Regions
• The "Maggie" filament: Physical properties of a giant atomic cloud
• Polarization of seven MBM clouds at high galactic latitude
• Probing the cold neutral medium through HI emission morphology with the scattering transform
• Turbulent power distribution in the local interstellar medium
• First look at the multiphase interstellar medium with synthetic observations of low-frequency Faraday tomography
• High-resolution HI and CO observations of high-latitude intermediate-velocity clouds
• Mapping the Thermal Condensation of Diffuse H I in the North Celestial Pole Loop
• A Comparison of Multi-Phase Magnetic Field Tracers in a High-Galactic Latitude Region of the Filamentary Interstellar Medium
• Interactions of a shock with a molecular cloud at various stages of its evolution due to thermal instability and gravity
• The physical and the geometrical properties of simulated cold HI structures
• C II radiative cooling of the Galactic diffuse interstellar medium: Insight about the star formation in Damped Lyman-alpha systems
• Aspect ratios of far-infrared and H i filaments in the diffuse interstellar medium at high Galactic latitudes
• Properties of atomic hydrogen gas in the Galactic plane from THOR 21-cm absorption spectra: a comparison with the high latitude gas
• The cold neutral medium in filaments at high Galactic latitudes
• Impact of the ambipolar diffusion in the structuration of the magnetic Rayleigh Taylor instability with oblique magnetic field
• Quantitative Morphology of Galactic Cirrus in Deep Optical Imaging
• Description of turbulent dynamics in the interstellar medium: Multifractal microcanonical analysis: II. Sparse filtering of Herschel observation maps and visualization of filamentary structures at different length scales
• JWST imaging of the Pleiades: anisotropy of turbulence in the cold neutral medium
• The role of neutral hydrogen in setting the abundances of molecular species in the Milky Way's diffuse interstellar medium. II. Comparison between observations and theoretical models
• Thermal instability and multiphase dynamics in the ISM with polybaric pressure effects
• The contribution of neutral gas to Faraday tomographic data at low frequencies. A first extensive comparison between real and synthetic data