On the distribution of the Cold Neutral Medium in galaxy discs

Abstract

The Cold Neutral Medium (CNM) is an important part of the galactic gas cycle and a precondition for the formation of molecular and star forming gas, yet its distribution is still not fully understood. In this work we present extremely high resolution simulations of spiral galaxies with time-dependent chemistry such that we can track the formation of the CNM, its distribution within the galaxy, and its correlation with star formation. We find no strong radial dependence between the CNM fraction and total HI due to the decreasing interstellar radiation field counterbalancing the decreasing gas column density at larger galactic radii.However, the CNM fraction does increase in spiral arms where the CNM distribution is clumpy, rather than continuous, overlapping more closely with H2. The CNM doesn't extend out radially as far as HI, and the vertical scale height is smaller in the outer galaxy compared to HI with no flaring. The CNM column density scales with total midplane pressure and disappears from the gas phase below values of PT/kB =1000 K/cm3. We find that the star formation rate density follows a similar scaling law with CNM column density to the total gas Kennicutt-Schmidt law. In the outer galaxy we produce realistic vertical velocity dispersions in the HI purely from galactic dynamics but our models do not predict CNM at the extremely large radii observed in HI absorption studies of the Milky Way. We suggest that extended spiral arms might produce isolated clumps of CNM at these radii.

arXiv comment13 pages, 20 figures, accepted by MNRAS

References in corpus (55)

• The Global Schmidt Law in Star Forming Galaxies
• Theory of Star Formation
• E pur si muove: Galiliean-invariant cosmological hydrodynamical simulations on a moving mesh
• The Star Formation Law in Nearby Galaxies on Sub-Kpc Scales
• The Spitzer c2d Legacy Results: Star Formation Rates and Efficiencies; Evolution and Lifetimes
• FIRE-2 Simulations: Physics versus Numerics in Galaxy Formation
• The Neutral Atomic Phases of the ISM in the Galaxy
• Modelling Accretion in Protobinary Systems
• The Millennium Arecibo 21-CM Absorption Line Survey. II. Properties of the Warm and Cold Neutral Media
• Simulations on a Moving Mesh: The Clustered Formation of Population III Protostars
• Modeling Collapse and Accretion in Turbulent Gas Clouds: Implementation and Comparison of Sink Particles in AMR and SPH
• The SILCC (SImulating the LifeCycle of molecular Clouds) project: I. Chemical evolution of the supernova-driven ISM
• A Herschel [CII] Galactic plane survey I: the global distribution of ISM gas components
• Simulating the formation of molecular clouds. I. Slow formation by gravitational collapse from static initial conditions
• Accretion-Driven Turbulence as Universal Process: Galaxies, Molecular Clouds, and Protostellar Disks
• A new Jeans resolution criterion for (M)HD simulations of self-gravitating gas: Application to magnetic field amplification by gravity-driven turbulence
• Simulating the formation of molecular clouds. II. Rapid formation from turbulent initial conditions
• The SILCC (SImulating the LifeCycle of molecular Clouds) project - II. Dynamical evolution of the supernova-driven ISM and the launching of outflows
• The supernova rate-velocity dispersion relation in the interstellar medium
• CO-dark gas and molecular filaments in Milky Way type galaxies
• Three Dimensional Hydrodynamic Simulations of Multiphase Galactic Disks with Star Formation Feedback: I. Regulation of Star Formation Rates
• Modelling the supernova-driven ISM in different environments
• Mapping metallicity variations across nearby galaxy disks
• NGC 2915. II. A Dark Spiral Galaxy With A Blue Compact Dwarf Core
• The COS/UVES Absorption Survey of the Magellanic Stream. III: Ionization, Total Mass, and Inflow Rate onto the Milky Way
• TreeCol: a novel approach to estimating column densities in astrophysical simulations
• Dynamical Equilibrium in the Molecular ISM in 28 Nearby Star-Forming Galaxies
• The distribution of atomic hydrogen in EAGLE galaxies: morphologies, profiles, and HI holes
• Revisiting the Integrated Star Formation Law. Paper I: Non-Starbursting Galaxies
• Volumetric star formation laws of disc galaxies
• The 21-SPONGE HI Absorption Line Survey II: The temperature of Galactic HI
• Simulations of magnetized multiphase galactic disk regulated by supernovae explosions
• SILCC VI -- Multi-phase ISM structure, stellar clustering, and outflows with supernovae, stellar winds, ionising radiation and cosmic rays
• The Cloud Factory I: Generating resolved filamentary molecular clouds from galactic-scale forces
• Saturated-State Turbulence and Structure from Thermal and Magnetorotational Instability in the ISM: Three-Dimensional Numerical Simulations
• Models of Vertically Stratified Two-Phase ISM Disks with MRI-Driven Turbulence
• Tracing the formation of molecular clouds via [CII], [CI] and CO emission
• Simulations of the star-forming molecular gas in an interacting M51-like galaxy
• The Galactic radial abundance gradients of C, N, O, Ne, S, Cl and Ar from deep spectra of H II regions
• On the Three-Dimensional Structure of Local Molecular Clouds
• The Outer Disk of the Milky Way Seen in 21-cm Absorption
• Approximations for modelling CO chemistry in GMCs: a comparison of approaches
• Thermal Phases of the Neutral Atomic Interstellar Medium -- from Solar Metallicity to Primordial Gas
• Physical Processes in Star Formation
• Properties of HI discs in the Auriga cosmological simulations
• The Interstellar Medium and Star Formation in Edge-On Galaxies. II. NGC 4157, 4565, and 5907
• Structure distribution and turbulence in self-consistently supernova-driven ISM of multiphase magnetized galactic discs
• The stellar population and interstellar medium in NGC 6822
• A simple method to convert sink particles into stars
• The history of dynamics and stellar feedback revealed by the HI filamentary structure in the disk of the Milky Way
• The Galactic dynamics revealed by the filamentary structure in atomic hydrogen emission
• On the Spatially Resolved Star Formation History in M51 I: Hybrid UV+IR Star Formation Laws and IR Emission from Dust Heated by Old Stars
• Simulations of the star-forming molecular gas in an interacting M51-like galaxy: cloud population statistics
• GASKAP Pilot Survey Science II: ASKAP Zoom Observations of Galactic 21-cm Absorption
• Is the molecular KS relationship universal down to low metallicities?

Cited by in corpus (1)

• Anisotropy in the carbon monoxide (CO) line emission across the Milky Way's disk