Star formation and molecular hydrogen in dwarf galaxies: a non-equilibrium view

Abstract

We study the connection of star formation to atomic (HI) and molecular hydrogen (H${}_2$) in isolated, low metallicity dwarf galaxies with high-resolution ($m_{\mathrm{gas}}$ = 4 M${}_{\odot }$, $N_{\mathrm{ngb}}$ = 100) SPH simulations. The model includes self-gravity, non-equilibrium cooling, shielding from an interstellar radiation field, the chemistry of H${}_2$ formation, H${}_2$-independent star formation, supernova feedback and metal enrichment. We find that the H${}_2$ mass fraction is sensitive to the adopted dust-to-gas ratio and the strength of the interstellar radiation field, while the star formation rate is not. Star formation is regulated by stellar feedback, keeping the gas out of thermal equilibrium for densities $n<$ 1 cm${}^{-3}$. Because of the long chemical timescales, the H${}_2$ mass remains out of chemical equilibrium throughout the simulation. Star formation is well-correlated with cold ( T $⩽$ 100 K ) gas, but this dense and cold gas - the reservoir for star formation - is dominated by HI, not H${}_2$. In addition, a significant fraction of H${}_2$ resides in a diffuse, warm phase, which is not star-forming. The ISM is dominated by warm gas (100 K $<$ T $⩽3\times 10^4$ K) both in mass and in volume. The scale height of the gaseous disc increases with radius while the cold gas is always confined to a thin layer in the mid-plane. The cold gas fraction is regulated by feedback at small radii and by the assumed radiation field at large radii. The decreasing cold gas fractions result in a rapid increase in depletion time (up to 100 Gyrs) for total gas surface densities ${\Sigma }_{\mathrm{HI}+{\mathrm{H}}_2}\lesssim$ 10 M${}_{\odot }$pc${}^{-2}$, in agreement with observations of dwarf galaxies in the Kennicutt-Schmidt plane.

Accepted for publication in MNRAS. Changes (including a pamameter study in Appendix C) highlighted

References in corpus (26)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• Introducing the Illustris Project: Simulating the coevolution of dark and visible matter in the Universe
• The effect of photo-ionization on the cooling rates of enriched, astrophysical plasmas
• Gas-to-Dust mass ratios in local galaxies over a 2 dex metallicity range
• Momentum Injection by Supernovae in the Interstellar Medium
• Modelling discontinuities and Kelvin-Helmholtz instabilities in SPH
• The SILCC (SImulating the LifeCycle of molecular Clouds) project: I. Chemical evolution of the supernova-driven ISM
• Inviscid SPH
• Simulating the formation of molecular clouds. I. Slow formation by gravitational collapse from static initial conditions
• Molecular Hydrogen and Global Star Formation Relations in Galaxies
• The Herschel Dwarf Galaxy Survey: I. Properties of the low-metallicity ISM from PACS spectroscopy
• The SILCC (SImulating the LifeCycle of molecular Clouds) project - II. Dynamical evolution of the supernova-driven ISM and the launching of outflows
• HI-to-H2 Transitions and H I Column Densities in Galaxy Star-Forming Regions
• An uncertainty principle for star formation. I. Why galactic star formation relations break down below a certain spatial scale
• The energy and momentum input of supernova explosions in structured and ionised molecular clouds
• Star Formation in Semi-Analytic Galaxy Formation Models with Multiphase Gas
• CO-dark gas and molecular filaments in Milky Way type galaxies
• The Atomic to Molecular Transition and its Relation to the Scaling Properties of Galaxy Disks in the Local Universe
• SPHGal: Smoothed Particle Hydrodynamics with improved accuracy for Galaxy simulations
• The equilibrium view on dust and metals in galaxies: Galactic outflows drive low dust-to-metal ratios in dwarf galaxies
• Dust origin in late-type dwarf galaxies: ISM growth vs. type II supernovae
• The ISM in spiral galaxies: can cooling in spiral shocks produce molecular clouds?
• A Star Formation Law for Dwarf Irregular Galaxies
• The spatially resolved Kennicutt-Schmidt relation in the HI dominated regions of spiral and dwarf irregular galaxies
• Massive stars formed in atomic hydrogen reservoirs: HI observations of gamma-ray burst host galaxies
• The effects of metallicity, UV radiation and non-equilibrium chemistry in high-resolution simulations of galaxies

Cited by in corpus (114)

• FIRE-2 Simulations: Physics versus Numerics in Galaxy Formation
• Theoretical Challenges in Galaxy Formation
• The Evolution of the Star-forming Interstellar Medium across Cosmic Time
• Simulating cosmic structure formation with the GADGET-4 code
• How To Model Supernovae in Simulations of Star and Galaxy Formation
• The Dawes Review 9: The role of cold gas stripping on the star formation quenching of satellite galaxies
• The SILCC project: III. Regulation of star formation and outflows by stellar winds and supernovae
• Feedback first: the surprisingly weak effects of magnetic fields, viscosity, conduction, and metal diffusion on galaxy formation
• Cooler and smoother -- the impact of cosmic rays on the phase structure of galactic outflows
• SILCC-Zoom: The dynamical and chemical evolution of molecular clouds
• Modelling Dust Evolution in Galaxies with a Multiphase, Inhomogeneous ISM
• Variable interstellar radiation fields in simulated dwarf galaxies: supernovae versus photoelectric heating
• Simulating an Isolated Dwarf Galaxy with Multi-Channel Feedback and Chemical Yields from Individual Stars
• The detailed structure and the onset of galaxy formation in low-mass gaseous dark matter haloes
• Modeling the atomic-to-molecular transition in cosmological simulations of galaxy formation
• Radiative Stellar Feedback in Galaxy Formation: Methods and Physics
• The GRIFFIN project -- Formation of star clusters with individual massive stars in a simulated dwarf galaxy starburst
• Supernova-driven winds in simulated dwarf galaxies
• Supernova feedback in numerical simulations of galaxy formation: separating physics from numerics
• Efficient early stellar feedback can suppress galactic outflows by reducing supernova clustering
• Simulations of the star-forming molecular gas in an interacting M51-like galaxy
• Chaos and Variance in Galaxy Formation
• H${}_2$-based star formation laws in hierarchical models of galaxy formation
• Thermal Phases of the Neutral Atomic Interstellar Medium -- from Solar Metallicity to Primordial Gas
• The formation of low metallicity globular clusters in dwarf galaxy mergers
• Post-Newtonian dynamical modeling of supermassive black holes in galactic-scale simulations
• A little FABLE: exploring AGN feedback in dwarf galaxies with cosmological simulations
• The formation of extremely diffuse galaxy cores by merging supermassive black holes
• Stellar Radiation is Critical for Regulating Star Formation and Driving Outflows in Low Mass Dwarf Galaxies
• Supernova-blast waves in wind-blown bubbles, turbulent, and power-law ambient media
• LYRA I: Simulating the multi-phase ISM of a dwarf galaxy with variable energy supernovae from individual stars
• The failure of stellar feedback, magnetic fields, conduction, and morphological quenching in maintaining red galaxies
• CO-dark molecular gas at high redshift: very large H${}_2$ content and high pressure in a low metallicity damped Lyman-alpha system
• The influence of environment on satellite galaxies in the GAEA semi-analytic model
• Metallicity dependence of the H/H${}_2$ and C${}^{+}$/C/CO distributions in a resolved self-regulating interstellar medium
• Suppression of star formation in dwarf galaxies by grain photoelectric feedback
• The HI-to-H2 Transition in a Turbulent Medium
• Physics of Galactic Metals: Evolutionary Effects due to Production, Distribution, Feedback & Interaction with Black Holes
• The natural emergence of the correlation between H2 and star formation rate surface densities in galaxy simulations
• A simple method to convert sink particles into stars
• On the Appearance of Thresholds in the Dynamical Model of Star Formation
• Photochemistry and Heating/Cooling of the Multiphase Interstellar Medium with UV Radiative Transfer for Magnetohydrodynamic Simulations
• A fundamental test for stellar feedback recipes in galaxy simulations
• On the origin of surprisingly cold gas discs in galaxies at high redshift
• Discrete Effects in Stellar Feedback: Individual Supernovae, Hypernovae, and IMF Sampling in Dwarf Galaxies
• Hot phase generation by supernovae: resolution, chemistry and thermal conduction
• The origin of the enhanced metallicity of satellite galaxies
• Cosmological simulations of dwarfs: the need for ISM physics beyond SN feedback alone
• INFERNO: Galactic winds in dwarf galaxies with star-by-star simulations including runaway stars
• 3D chemical structure of diffuse turbulent ISM. I. Statistics of the HI-to-H${}_2$ transition
• The challenge of simulating the star cluster population of dwarf galaxies with resolved interstellar medium
• A chemical model for the interstellar medium in galaxies
• The volumetric star formation law for nearby galaxies -- Extension to dwarf galaxies and low-density regions
• The [CII]--SFR correlation in dwarf galaxies across cosmic time
• GRB 980425 host: [CII], [OI] and CO lines reveal recent enhancement of star formation due to atomic gas inflow
• Modeling for Stellar Feedback in Galaxy Formation Simulations
• Code Comparison in Galaxy Scale Simulations with Resolved Supernova Feedback: Lagrangian vs. Eulerian Methods
• RIGEL: Simulating dwarf galaxies at solar mass resolution with radiative transfer and feedback from individual massive stars
• Pre-supernova feedback sets the star cluster mass function to a power law and reduces the cluster formation efficiency
• Spatial Decorrelation of Young Stars and Dense Gas as a Probe of the Star Formation-Feedback Cycle in Galaxies
• A simple model for molecular hydrogen chemistry coupled to radiation hydrodynamics
• The effect of non-equilibrium metal cooling on the interstellar medium
• The formation of massive stellar clusters in converging galactic flows with photoionisation
• Formation of star clusters and enrichment by massive stars in simulations of low-metallicity galaxies with a fully sampled initial stellar mass function
• The Elephant in the Room: The Importance of Where and When Massive Stars Form in Molecular Clouds
• The in situ formation of molecular and warm ionised gas triggered by hot outflows
• Gas flows in the circumgalactic medium around simulated high-redshift galaxies
• Structure and rotation of young massive star clusters in a simulated dwarf starburst
• PDFchem: A new fast method to determine ISM properties and infer environmental parameters using probability distributions
• Populating H${}_2$ and CO in galaxy simulation with dust evolution
• Molecular gas masses of gamma-ray burst host 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
• Dark influences III. Structural characterization of minor mergers of dwarf galaxies with dark satellites
• Less wrong: a more realistic initial condition for simulations of turbulent molecular clouds
• Star clusters forming in a low metallicity starburst -- rapid self-enrichment by (very) massive stars
• The SATIN project I: Turbulent multi-phase ISM in Milky Way simulations with SNe feedback from stellar clusters
• Chemical evolution of giant molecular clouds in simulations of galaxies
• The origin of the [CII]-deficit in a simulated dwarf galaxies starburst
• The In-situ Origins of Dwarf Stellar Outskirts in FIRE-2
• Why are thermally- and cosmic ray-driven galactic winds fundamentally different?
• EDGE-INFERNO: Simulating every observable star in faint dwarf galaxies and their consequences for resolved-star photometric surveys
• The effects of local stellar radiation and dust depletion on non-equilibrium interstellar chemistry
• Magnetic fields do not suppress global star formation in low metallicity dwarf galaxies
• Chemical post-processing of magneto-hydrodynamical simulations of star-forming regions: robustness and pitfalls
• The complete census of molecular hydrogen in a simulated disc galaxy
• Effects of dust evolution on the abundances of CO and H${}_2$
• Timescales for Hi consumption and SFR depletion of satellite galaxies in groups
• Mechanical feedback from stellar winds with an application to galaxy formation at high redshift
• Is the molecular KS relationship universal down to low metallicities?
• The Column Densities of Molecular Gas across Cosmic Time: Bridging Observations and Simulations
• A panchromatic view of star cluster formation in a simulated dwarf galaxy starburst
• WVTICs -- SPH initial conditions for everyone
• Mergers all the way down: stellar collisions and kinematics of a dense hierarchically forming massive star cluster in a dwarf starburst
• Relativistic supernova 2009bb exploded close to an atomic gas cloud
• Outskirts of Nearby Disk Galaxies: Star Formation and Stellar Populations
• Resolution criteria to avoid artificial clumping in Lagrangian hydrodynamic simulations with a multi-phase interstellar medium
• Numerical dependencies of the galactic dynamo in isolated galaxies with SPH
• A comparison of ${\text{H}}_2$ formation models at high redshift
• Modeling molecular hydrogen in low metallicity galaxies
• Modelling H${}_2$ and its effects on star formation using a joint implementation of GADGET-3 and KROME
• The impact of cosmic ray heating on the cooling of the low-metallicity interstellar medium
• Photoelectric heating effects on the evolution of luminous disk galaxies
• The Noctua Suite of Simulations -- The Difficulty of Growing Massive Black Holes in Low-Mass Dwarf Galaxies
• Early Science with the Large Millimeter Telescope: discovery of the 12CO(1-0) emission line in the ring galaxy, VIIZw466
• A study of outer disk stellar populations of face-on star-forming galaxies in SDSS-IV MaNGA: causes of H$\alpha$ deficiency
• Applying a star formation model calibrated on high-resolution interstellar medium simulations to cosmological simulations of galaxy formation
• Auriga Superstars: Improving the resolution and fidelity of stellar dynamics in cosmological galaxy simulations
• Interpreting Millimeter Emission from IMEGIN galaxies NGC 2146 and NGC 2976
• Quokka-based understanding of outflows (QED) -- II. X-ray metallicity gradients as a signature of galactic wind metal loading
• Numerical Methods for Simulating Star Formation
• SILCC -- IX. The multi-phase interstellar medium at low metallicity
• LYRA II: Cosmological dwarf galaxy formation with inhomogeneous Population III enrichment
• Supernovae and photoionizing feedback in spiral arm molecular clouds