Simulating the formation of molecular clouds. I. Slow formation by gravitational collapse from static initial conditions

Abstract

We study the formation of H2 in the ISM, using a modified version of the astrophysical magnetohydrodynamical code ZEUS-MP that includes a non-equilibrium treatment of the formation and destruction of H2. We examine two different approximations to treat the shielding of H2 against photodissociation: a local approximation, which gives us a solid lower bound on the amount of shielding, and a method based on ray-tracing that is considerably more accurate in some circumstances but that produces results that are harder to clearly interpret. Either approximation allows one to perform three-dimensional high-resolution simulations of cloud formation with only modest computational resources. We also include a detailed treatment of the thermal behaviour of the gas. In this paper, we focus on the problem of molecular cloud formation in gravitationally unstable, initially static gas. We show that in these conditions, and for initial densities consistent with those observed in the cold, neutral atomic phase of the interstellar medium, H2 formation occurs on a timescale t > 10 Myr, comparable to or longer than the gravitational free-fall timescale of the cloud. We also show that the collapsing gas very quickly reaches thermal equilibrium and that the equation of state of the gas is generally softer than isothermal. Finally, we demonstrate that although these results show little sensitivity to variations in most of our simulation parameters, they are highly sensitive to the assumed initial density n_i. Reducing n_i significantly increases the cloud formation timescale and decreases the amount of hydrogen ultimately converted to H2. (Abridged).

arXiv comment89 pages, 40 figures, AASTex. Results section significantly revised and extended. Includes results from a large number of new simulations performed using a treatment of H2 photodissociation based on ray-tracing. This version matches that accepted by ApJS

References in corpus (48)

• Control of star formation by supersonic turbulence
• The Neutral Atomic Phases of the ISM in the Galaxy
• Structure of Stationary Photodissociation Fronts
• Simulations of Early Structure Formation: Primordial Gas Clouds
• Rapid Formation of Molecular Clouds and Stars in the Solar Neighborhood
• Star Formation in a Crossing Time
• Dissipation in Compressible MHD Turbulence
• Modelling Primordial Gas in Numerical Cosmology
• The Energy Dissipation Rate of Supersonic, Magnetohydrodynamic Turbulence in Molecular Clouds
• Velocity Modification of HI Power Spectrum
• An Origin of Supersonic Motions in Interstellar Clouds
• Galactic and extragalactic magnetic fields
• Enhanced cosmic-ray flux toward zeta Persei inferred from laboratory study of H3+ - e- recombination rate
• Molecular Hydrogen Formation on Astrophysically Relevant Surfaces
• On the Role of Massive Stars in the Support and Destruction of Giant Molecular Clouds
• Simulating Radiating and Magnetized Flows in Multi-Dimensions with ZEUS-MP
• The stellar mass spectrum from non-isothermal gravoturbulent fragmentation
• Turbulent Flow-Driven Molecular Cloud Formation: A Solution to the Post-T Tauri Problem?
• Turbulent Structure of a Stratified Supernova-Driven Interstellar Medium
• Simulating the formation of molecular clouds. II. Rapid formation from turbulent initial conditions
• Molecular Cloud Formation in Shock-Compressed Layers
• On the Origin of the Global Schmidt Law of Star Formation
• SCUBA Polarization Measurements of the Magnetic Field Strengths in the L183, L1544, and L43 Prestellar Cores
• Molecular Cloud Formation Behind Shock Waves
• The Global Evolution of Giant Molecular Clouds. I: Model Formulation and Quasi-Equilibrium Behavior
• Modeling the Warm Ionized Interstellar Medium and Its Impact on Elemental Abundance Studies
• Disk-Halo Interaction - I. Three-Dimensional Evolution of the Galactic Disk
• Volume Filling Factors of the ISM Phases in Star Forming Galaxies - I. The Role of the Disk-Halo Interaction
• Towards simulating star formation in the interstellar medium
• Electron-Ion Recombination on Grains and Polycyclic Aromatic Hydrocarbons
• Three-Dimensional Simulations of Parker, Magneto-Jeans, and Swing Instabilities in Shearing Galactic Gas Disks
• Thermal Instability-Induced Interstellar Turbulence
• Radiation Driven Implosion of Molecular Cloud Cores
• The Field Condition: A New Constraint of Spatial Resolution in Simulations of the nonlinear Development of Thermal Instability
• The Polytropic Equation of State of Interstellar Gas Clouds
• Generation of Magnetic Fields in the Multi-phase ISM with Supernova-Driven Turbulence
• Star Formation in Isolated Disk Galaxies. I. Models and Characteristics of Nonlinear Gravitational Collapse
• The Formation of Molecular Clouds
• Physical conditions in QSO absorbers from fine-structure absorption lines
• The Ionization Fraction in Dense Molecular Gas II: Massive Cores
• Gas-phase recombination, grain neutralization and cosmic-ray ionization in diffuse gas
• Confinement-Driven Spatial Variations in the Cosmic Ray Flux
• Comparing gas-phase and grain-catalyzed H2 formation
• Rarefaction Shocks, Shock Errors and Low Order of Accuracy in ZEUS
• The Three-Dimensional Structure of a Massive Gas Disk in the Galactic Central Region
• Scaling Relations for Turbulence in the Multiphase Interstellar Medium
• Hydrodynamical simulations of the decay of high-speed molecular turbulence. I. Dense molecular regions
• Interstellar Phase Transitions Stimulated by Time-dependent Heating

Cited by in corpus (236)

• The CO-to-H2 Conversion Factor
• Comparing the statistics of interstellar turbulence in simulations and observations: Solenoidal versus compressive turbulence forcing
• The Star Formation Rate of Turbulent Magnetized Clouds: Comparing Theory, Simulations, and Observations
• Analytical theory for the initial mass function: CO clumps and prestellar cores
• The Birth of a Galaxy: Primordial Metal Enrichment and Stellar Populations
• Phantom: A smoothed particle hydrodynamics and magnetohydrodynamics code for astrophysics
• On the Star Formation Efficiency of Turbulent Magnetized Clouds
• The SILCC (SImulating the LifeCycle of molecular Clouds) project: I. Chemical evolution of the supernova-driven ISM
• Turbulent molecular clouds
• The Big Problems in Star Formation: the Star Formation Rate, Stellar Clustering, and the Initial Mass Function
• Molecular Hydrogen and Global Star Formation Relations in Galaxies
• Star Formation in Disk Galaxies. I. Formation and Evolution of Giant Molecular Clouds via Gravitational Instability and Cloud Collisions
• On the Relationship Between Molecular Hydrogen and Carbon Monoxide Abundances in Molecular Clouds
• Modeling Molecular Hydrogen and Star Formation in Cosmological Simulations
• The SILCC (SImulating the LifeCycle of molecular Clouds) project - II. Dynamical evolution of the supernova-driven ISM and the launching of outflows
• Environmental Dependence of the Kennicutt-Schmidt Relation in Galaxies
• Photodissociation of H2 in Protogalaxies: Modeling Self-Shielding in 3D Simulations
• CO-dark gas and molecular filaments in Milky Way type galaxies
• The SILCC project: III. Regulation of star formation and outflows by stellar winds and supernovae
• In-N-Out: the gas cycle from dwarfs to spiral galaxies
• Modeling CO Emission: I. CO as a Column Density Tracer and the X-Factor in Molecular Clouds
• The Exciting Lives of Giant Molecular Clouds
• Star formation at very low metallicity. I: Chemistry and cooling at low densities
• On the nature of star-forming filaments: I. Filament morphologies
• Modeling jet and outflow feedback during star cluster formation
• Analytical theory for the initial mass function: II. Properties of the flow
• Implementing Molecular Hydrogen in Hydrodynamic Simulations of Galaxy Formation
• Modelling CO formation in the turbulent interstellar medium
• Modelling the supernova-driven ISM in different environments
• Driving Turbulence and Triggering Star Formation by Ionizing Radiation
• Star formation and molecular hydrogen in dwarf galaxies: a non-equilibrium view
• Formation of Turbulent and Magnetized Molecular Clouds via Accretion Flows of HI Clouds
• Molecular Cloud Evolution IV: Magnetic Fields, Ambipolar Diffusion, and the Star Formation Efficiency
• Modeling CO Emission: II. The Physical Characteristics that Determine the X factor in Galactic Molecular Clouds
• Rapid Molecular Cloud and Star Formation: Mechanisms and Movies
• Cooler and smoother -- the impact of cosmic rays on the phase structure of galactic outflows
• On the nature of star-forming filaments: II. Sub-filaments and velocities
• GMC formation by agglomeration and self gravity
• The role of cosmic ray pressure in accelerating galactic outflows
• SILCC-Zoom: The dynamical and chemical evolution of molecular clouds
• Modelling Dust Evolution in Galaxies with a Multiphase, Inhomogeneous ISM
• How long does it take to form a molecular cloud?
• Star formation in metal-poor gas clouds
• Variable interstellar radiation fields in simulated dwarf galaxies: supernovae versus photoelectric heating
• The frequency and nature of `cloud-cloud collisions' in galaxies
• 3D-PDR: A new three-dimensional astrochemistry code for treating Photodissociation Regions
• The equilibrium view on dust and metals in galaxies: Galactic outflows drive low dust-to-metal ratios in dwarf galaxies
• Star Formation Efficiency and Dispersal of Giant Molecular Clouds with UV Radiation Feedback: Dependence on Gravitational Boundedness and Magnetic Fields
• The Effects of Accretion Luminosity upon Fragmentation in the Early Universe
• The density structure and star formation rate of non-isothermal polytropic turbulence
• Analytical theory for the initial mass function: III time dependence and star formation rate
• A Simple and Accurate Network for Hydrogen and Carbon Chemistry in the ISM
• Supernova-driven winds in simulated dwarf galaxies
• The GRIFFIN project -- Formation of star clusters with individual massive stars in a simulated dwarf galaxy starburst
• SILCC VI -- Multi-phase ISM structure, stellar clustering, and outflows with supernovae, stellar winds, ionising radiation and cosmic rays
• The SILCC project --- IV. Impact of dissociating and ionising radiation on the interstellar medium and Halpha emission as a tracer of the star formation rate
• Simulations of the Milky Way's central molecular zone -- I. Gas dynamics
• Star Formation in Disk Galaxies. II. The Effect of Star Formation and Photoelectric Heating on the Formation and Evolution of Giant Molecular Clouds
• The Cloud Factory I: Generating resolved filamentary molecular clouds from galactic-scale forces
• The relative impact of photoionizing radiation and stellar winds on different environments
• The ISM in spiral galaxies: can cooling in spiral shocks produce molecular clouds?
• Is atomic carbon a good tracer of molecular gas in metal-poor galaxies?
• Tracing the formation of molecular clouds via [CII], [CI] and CO emission
• StarBench: The D-type expansion of an HII region
• Simulations of the star-forming molecular gas in an interacting M51-like galaxy
• Modelling [CI] emission from turbulent molecular clouds
• Star Formation in the First Galaxies I: Collapse Delayed by Lyman-Werner Radiation
• Approximations for modelling CO chemistry in GMCs: a comparison of approaches
• A theoretical explanation for the Central Molecular Zone asymmetry
• The environmental dependence of the X_CO conversion factor
• Synthetic C${}^{18}$O observations of fibrous filaments: the problems of mapping from PPV to PPP
• Tree-based solvers for adaptive mesh refinement code FLASH - I: gravity and optical depths
• Evidence for a non-universal Kennicutt-Schmidt relationship using hierarchical Bayesian linear regression
• The formation of low metallicity globular clusters in dwarf galaxy mergers
• Pressure Relations and Vertical Equilibrium in the Turbulent, Multiphase ISM
• The art of modeling CO, [CI], and [CII] in cosmological galaxy formation models
• The X_CO conversion factor from galactic multiphase ISM simulations
• The SILCC project - V. The impact of magnetic fields on the chemistry and the formation of molecular clouds
• A physical model for the [CII]-FIR deficit in luminous galaxies
• The morphology of the Milky Way - I. Reconstructing CO maps from simulations in fixed potentials
• H2 distribution during formation of multiphase molecular clouds
• Metallicity dependence of the H/H${}_2$ and C${}^{+}$/C/CO distributions in a resolved self-regulating interstellar medium
• On column density thresholds and the star formation rate
• The Necessity of Feedback Physics in Setting the Peak of the Initial Mass Function
• The geometry of the gas surrounding the Central Molecular Zone: on the origin of localised molecular clouds with extreme velocity dispersions
• Modeling H2 formation in the turbulent ISM: Solenoidal versus compressive turbulent forcing
• Using CO line ratios to trace the physical properties of molecular clouds
• Giant Molecular clouds: what are they made from, and how do they get there?
• Molecular gas, CO, and star formation in galaxies: emergent empirical relations, feedback, and the evolution of very gas-rich systems
• Histogram of oriented gradients: a technique for the study of molecular cloud formation
• Introducing TIGRESS-NCR: I. Co-Regulation of the Multiphase Interstellar Medium and Star Formation Rates
• The star formation efficiency and its relation to variations in the initial mass function
• Fervent: Chemistry-coupled, ionising and non-ionising radiative feedback in magnetohydrodynamical simulations
• SILCC-ZOOM: The early impact of ionizing radiation on forming molecular clouds
• Chemistry and radiative shielding in star forming galactic disks
• Simulating the interstellar medium of galaxies with radiative transfer, non-equilibrium thermochemistry, and dust
• SILCC VII -- Gas kinematics and multiphase outflows of the simulated ISM at high gas surface densities
• The effect of models of the interstellar media on the central mass distribution of galaxies
• Photochemistry and Heating/Cooling of the Multiphase Interstellar Medium with UV Radiative Transfer for Magnetohydrodynamic Simulations
• How an improved implementation of H2 self-shielding influences the formation of massive stars and black holes
• The role of galactic dynamics in shaping the physical properties of giant molecular clouds in Milky Way-like galaxies
• The CO-to-H2 Conversion Factor across the Perseus Molecular Cloud
• CO line ratios in molecular clouds: the impact of environment
• The morphology of the Milky Way - II. Reconstructing CO maps from disc galaxies with live stellar distributions
• CO-dark gas and molecular filaments in Milky Way-type galaxies - II: The temperature distribution of the gas
• Mapping the core mass function to the initial mass function
• Does the CO-to-H2 conversion factor depend on the star formation rate?
• Hot phase generation by supernovae: resolution, chemistry and thermal conduction
• How well does CO emission measure the H${}_2$ mass of MCs?
• Momentum feedback from marginally-resolved HII regions in isolated disc galaxies
• Gravitational torques imply molecular gas inflow towards the nucleus of M51
• Dependence of $X_{\mathrm{CO}}$ on metallicity, intensity, and spatial scale in a self-regulated interstellar medium
• Efficacy of early stellar feedback in low gas surface density environments
• Gas and Dust in the Taffy Galaxies: Ugc12914/15
• GMC Collisions as Triggers of Star Formation. I. Parameter Space Exploration with 2D Simulations
• Eventful Evolution of Giant Molecular Clouds in Dynamically Evolving Spiral Arms
• The challenge of simulating the star cluster population of dwarf galaxies with resolved interstellar medium
• TORUS-3DPDR: A self-consistent code treating three-dimensional photoionization and photodissociation regions
• The roles of stellar feedback and galactic environment in star forming molecular clouds
• Star Formation in Molecular Clouds
• Synthetic observations of star formation and the interstellar medium
• Shock-triggered formation of magnetically-dominated clouds
• Multitracer cosmological line intensity mapping mock lightcone simulation
• Combining radiative transfer and diffuse interstellar medium physics to model star formation
• Collective outflow from a small multiple stellar system
• WIMP DM and first stars: suppression of fragmentation in primordial star formation
• Modeling the Atomic-to-Molecular Transition and Chemical Distributions of Turbulent Star-Forming Clouds
• Synthetic [CII] emission maps of a simulated molecular cloud in formation
• Code Comparison in Galaxy Scale Simulations with Resolved Supernova Feedback: Lagrangian vs. Eulerian Methods
• Three-dimensional molecular line transfer: A simulated star-forming region
• Protostellar Feedback in Turbulent Fragmentation: Consequences for Stellar Clustering and Multiplicity
• Direct collapse to supermassive black hole seeds: the critical conditions for suppression of ${\mathrm{H}}_2$ cooling
• A simple model for molecular hydrogen chemistry coupled to radiation hydrodynamics
• Synthetic CO, H2 and HI surveys of the Galactic 2nd Quadrant, and the properties of molecular gas
• Kiloparsec-Scale Simulations of Star Formation in Disk Galaxies. I. The unmagnetized and zero-feedback limit
• Gas velocity patterns in simulated galaxies: Observational diagnostics of spiral structure theories
• Dynamical Expansion of H II Regions from Ultracompact to Compact Sizes in Turbulent, Self-Gravitating Molecular Clouds
• On the resolution requirements for modelling molecular gas formation in solar neighbourhood conditions
• Non-Equilibrium Chemistry and Destruction of CO by X-ray Flares
• Is it possible to reconcile extragalactic IMF variations with a universal Milky Way IMF?
• Cloud formation in colliding flows: influence of the choice of cooling function
• Structure and rotation of young massive star clusters in a simulated dwarf starburst
• The in situ formation of molecular and warm ionised gas triggered by hot outflows
• Simulating the H2 content of high-redshift galaxies
• The Galactic Census of High- and Medium-mass Protostars. IV. Molecular Clump Radiative Transfer, Mass Distributions, Kinematics, and Dynamical Evolution
• Chemulator: Fast, accurate thermochemistry for dynamical models through emulation
• The formation and early evolution of embedded star clusters in spiral galaxies
• Magnetic field morphology and evolution in the Central Molecular Zone and its effect on gas dynamics
• A semi-analytic model of the turbulent multi-phase interstellar medium
• A scaling relation for the molecular cloud lifetime in Milky Way-like galaxies
• Star formation efficiencies of molecular clouds in a galactic center environment
• The role of initial magnetic field structure in the launching of protostellar jets
• Photoionising feedback in spiral arm molecular clouds
• On the accuracy of HI observations in molecular clouds -- More cold HI than thought?
• Dark Molecular Gas in Simulations of z~0 Disc Galaxies
• Co-evolution of Dust and Chemistry in Galaxy Simulations with a Resolved Interstellar Medium
• The formation of clusters and OB associations in different density spiral arm environments
• Synthetic observations of molecular clouds in a galactic center environment: I. Studying maps of column density and integrated intensity
• Star Formation in a Turbulent Framework: From Giant Molecular Clouds to Protostars
• Impact of supernova and cosmic-ray driving on the surface brightness of the galactic halo in soft X-rays
• How Cosmic Rays Mediate the Evolution of the Interstellar Medium
• Comparing Models for IMF Variation Across Cosmological Time in Milky Way-like Galaxies
• Interstellar MHD Turbulence and Star Formation
• Alignment of the magnetic field in star forming regions and why it might be difficult to observe
• Impact of an accurate modeling of primordial chemistry in high resolution studies
• The Early Stage of Molecular Cloud Formation by Compression of Two-phase Atomic Gases
• Chemical evolution of giant molecular clouds in simulations of galaxies
• The origin of the [CII]-deficit in a simulated dwarf galaxies starburst
• The properties, origin and evolution of stellar clusters in galaxy simulations and observations
• Atomic Chemistry in Turbulent Astrophysical Media II: Effect of the Redshift Zero Metagalactic Background
• Dense Regions in Supersonic Isothermal Turbulence
• Synthetic Large-Scale Galactic Filaments -- on their Formation, Physical Properties, and Resemblance to Observations
• Centroid Velocity Statistics of Molecular Clouds
• Stellar winds and photoionization in a spiral arm
• Radiation transport methods in star formation simulations
• The turbulent life of dust grains in the supernova-driven, multi-phase interstellar medium
• The Cloud Factory II: Gravoturbulent Kinematics of Resolved Molecular Clouds in a Galactic Potential
• The impact of magnetic fields on the chemical evolution of the supernova-driven ISM
• Principal Component Analysis of Molecular Clouds: Can CO reveal the dynamics?
• Star cluster formation and feedback in different environments of a Milky Way-like galaxy
• Unravelling the structure of magnetised molecular clouds with SILCC-Zoom: sheets, filaments and fragmentation
• The alignment is in their stars: on the spin-alignment of stars in star clusters
• Synthetic observations of spiral arm tracers of a simulated Milky Way analog
• Synthetic HI observations of a simulated spiral galaxy
• Building the molecular cloud population: the role of cloud mergers
• On the distribution of the Cold Neutral Medium in galaxy discs
• The role of previous generations of stars in triggering star formation and driving gas dynamics
• On the evolution of the observed Mass-to-Length relationship for star-forming filaments
• The Column Densities of Molecular Gas across Cosmic Time: Bridging Observations and Simulations
• The evolution of HCO${}^{+}$ in molecular clouds using a novel chemical post-processing algorithm
• Non-Equilibrium Abundances Treated Holistically (NEATH): the molecular composition of star-forming clouds
• Cosmic-ray-induced H${}_2$ line emission: Astrochemical modeling and implications for JWST observations
• Do simulated molecular clouds look like real ones?
• Structure analysis of simulated molecular clouds with the Delta-variance
• How do supernova remnants cool? -- I. Morphology, optical emission lines, and shocks
• Cloud properties across spatial scales in simulations of the interstellar medium
• Effective viscosity from cloud-cloud collisions in three-dimensional global SPH simulations
• Mergers all the way down: stellar collisions and kinematics of a dense hierarchically forming massive star cluster in a dwarf starburst
• AGN Outflow Shocks on Bonnor-Ebert Spheres
• On the Origin of the High Star-Formation Efficiency in Massive Galaxies at Cosmic Dawn
• Tree-based solvers for adaptive mesh refinement code FLASH -- III: a novel scheme for radiation pressure on dust and gas and radiative transfer from diffuse sources
• HYACINTH: HYdrogen And Carbon chemistry in the INTerstellar medium in Hydro simulations
• Implementing Dust Shielding as a Criteria for Star Formation
• Escaping the maze: a statistical sub-grid model for cloud-scale density structures in the interstellar medium
• CO enhancement by magnetohydrodynamic waves; Striations in the Polaris Flare
• Simulated [CII] in high-z galaxies
• The Astrochemical Evolution of Turbulent Giant Molecular Clouds : I - Physical Processes and Method of Solution for Hydrodynamic, Embedded Starless Clouds
• The impact of cosmic ray heating on the cooling of the low-metallicity interstellar medium
• The Noctua Suite of Simulations -- The Difficulty of Growing Massive Black Holes in Low-Mass Dwarf Galaxies
• Decaying turbulence in molecular clouds: how does it affect filament networks and star formation?
• Different molecular filament widths as tracers of accretion onto filaments
• A deep-learning approach to the 3D reconstruction of dust density and temperature in star-forming regions
• The role of shocks and the velocity gradient in the relative orientation of the magnetic field and dense gas clouds
• Line emission from filaments in molecular clouds
• An analytic formalism to describe the $N_{\mathrm{eff}}(\mathrm{H})$-$n_{\mathrm{H}}$ relationship in molecular clouds
• Binary outflows from young stars: interaction of co-orbital jet and wind
• Gas and star kinematics in cloud-cloud collisions
• A study of outer disk stellar populations of face-on star-forming galaxies in SDSS-IV MaNGA: causes of H$\alpha$ deficiency
• Dust destruction by the supernova remnant forward shock in a turbulent interstellar medium
• Ionisation in Turbulent Magnetic Molecular Clouds I. Effect on Density and Mass-to-Flux Ratio Structures
• Rotation measure and synchrotron emission signatures in simulations of magnetized galactic discs
• The origin and evolution of the [CII] deficit in HII regions and star-forming molecular clouds
• Tree-based solvers for adaptive mesh refinement code FLASH -- IV: An X-ray radiation scheme to couple discrete and diffuse X-ray emission sources to the thermochemistry of the interstellar medium
• Stellar initial mass function variation in massive early-type galaxies: the potential role of the deuterium abundance
• A multi-ion non-equilibrium solver for ionised astrophysical plasmas with arbitrary elemental abundances
• The nature of a primary jet within a circumbinary disc outflow in a young stellar system
• High$-z$ [OI] emission lines: ColdSIM simulations and ALMA observations
• Does the HCN/CO ratio trace the star-forming fraction of gas? II. Variations in CO and HCN Emissivity
• Protostellar disc structure and dynamics during star formation from cloud-scale initial conditions
• Gas dynamics in whole galaxies: SPH
• SILCC -- IX. The multi-phase interstellar medium at low metallicity
• Using synthetic emission maps to constrain the structure of the Milky Way
• Magnetic fields in star forming environments: how does field strength affect gas on spiral arm and cloud scales?
• Supernovae and photoionizing feedback in spiral arm molecular clouds
• Chemical Evolution of Turbulent Multiphase Molecular Clouds
• On the scale-height of the molecular gas disc in Milky Way-like galaxies