Dynamical cooling of galactic discs by molecular cloud collisions -- Origin of giant clumps in gas-rich galaxy discs

Abstract

Different from Milky-Way-like galaxies, discs of gas-rich galaxies are clumpy. It is believed that the clumps form because of gravitational instability. However, a necessary condition for gravitational instability to develop is that the disc must dissipate its kinetic energy effectively, this energy dissipation (also called cooling) is not well-understood. We propose that collisions (coagulation) between molecular clouds dissipate the kinetic energy of the discs, which leads to a dynamical cooling. The effectiveness of this dynamical cooling is quantified by the dissipation parameter $D$, which is the ratio between the free-fall time $t_{\mathrm{ff}}\approx 1/\sqrt{G{\rho }_{\mathrm{disc}}}$ and the cooling time determined by the cloud collision process $t_{\mathrm{cool}}$. This ratio is related to the ratio between the mean surface density of the disc ${\Sigma }_{\mathrm{disc}}$ and the mean surface density of molecular clouds in the disc ${\Sigma }_{\mathrm{cloud}}$. When $D<1/3$ (which roughly corresponds to ${\Sigma }_{\mathrm{disc}}<1/3{\Sigma }_{\mathrm{cloud}}$), cloud collision cooling is inefficient, and fragmentation is suppressed. When $D>1/3$ (which roughly corresponds to ${\Sigma }_{\mathrm{disc}}>1/3{\Sigma }_{\mathrm{cloud}}$), cloud-cloud collisions lead to a rapid cooling through which clumps form. On smaller scales, cloud-cloud collisions can drive molecular cloud turbulence. This dynamical cooling process can be taken into account in numerical simulations as a subgrid model to simulate the global evolution of disc galaxies.

arXiv commentMNRAS accepted

References in corpus (89)

• How Do Galaxies Get Their Gas?
• Control of star formation by supersonic turbulence
• Cold streams in early massive hot haloes as the main mode of galaxy formation
• The SINS survey: SINFONI Integral Field Spectroscopy of z ~ 2 Star-forming Galaxies
• Formation of Massive Galaxies at High Redshift: Cold Streams, Clumpy Disks and Compact Spheroids
• Nonlinear Outcome of Gravitational Instability in Cooling, Gaseous Disks
• High molecular gas fractions in normal massive star forming galaxies in the young Universe
• The SINS survey of z~2 galaxy kinematics: properties of the giant star forming clumps
• Re-examining Larson's Scaling Relationships in Galactic Molecular Clouds
• From rings to bulges: evidence for rapid secular galaxy evolution at z~2 from integral field spectroscopy in the SINS survey
• The Statistics of Supersonic Isothermal Turbulence
• Galaxy morphology to I=25 mag in the Hubble Deep Field
• The Atomic to Molecular Transition in Galaxies. II: HI and H_2 Column Densities
• Physical Properties and Galactic Distribution of Molecular Clouds identified in the Galactic Ring Survey
• Accretion-Driven Turbulence as Universal Process: Galaxies, Molecular Clouds, and Protostellar Disks
• The Structure of the Interstellar Medium of Star Forming Galaxies
• A Morphological Catalog of Galaxies in the Hubble Deep Field
• Stellar Populations in Ten Clump-Cluster Galaxies of the Ultra Deep Field
• A Characteristic Scale for Cold Gas
• The ISM in distant star-forming galaxies: Turbulent pressure, fragmentation and cloud scaling relations in a dense gas disk at z=2.3
• The PdBI Arcsecond Whirlpool Survey (PAWS). I. A Cloud-Scale/Multi-Wavelength View of the Interstellar Medium in a Grand-Design Spiral Galaxy
• Three-Dimensional Distribution of the ISM in the Milky Way Galaxy: II. The Molecular Gas Disk
• Clumpy Galaxies in CANDELS. I. The Definition of UV Clumps and the Fraction of Clumpy Galaxies at 0.5<z<3
• Global Star Formation Rates in Disk Galaxies and Circumnuclear Starbursts from Cloud Collisions
• The Luminosity, Stellar Mass, and Number Density Evolution of Field Galaxies of Known Morphology from z = 0.5 - 3
• The Atomic to Molecular Transition in Galaxies. I: An Analytic Approximation for Photodissociation Fronts in Finite Clouds
• HI-to-H2 Transitions and H I Column Densities in Galaxy Star-Forming Regions
• Faintest Galaxy Morphologies from $HST$ WFPC2 Imaging of the Hawaii Survey Fields
• Stellar Feedback in Molecular Clouds and its Influence on the Mass Function of Young Star Clusters
• CO-dark gas and molecular filaments in Milky Way type galaxies
• Clumpy Galaxies in GOODS and GEMS: Massive Analogs of Local Dwarf Irregulars
• Nonlinear Outcome of Gravitational Instability in Disks with Realistic Cooling
• Gravity-driven Turbulence in Galactic Disks
• A General Theory of Turbulent Fragmentation
• Discovery of Face-On Counterparts of Chain Galaxies in the Tadpole ACS Field
• Large-scale filaments associated with Milky Way spiral arms
• Giant Molecular Filaments in the Milky Way
• The Bones of the Milky Way
• The effective stability parameter for two-component galactic discs: Is 1/Q ~ 1/Q_stars + 1/Q_gas ?
• Formation of Spiral-Arm Spurs and Bound Clouds in Vertically Stratified Galactic Gas Disks
• Balance among gravitational instability, star formation, and accretion determines the structure and evolution of disk galaxies
• GMC formation by agglomeration and self gravity
• A complete 12CO 2-1 map of M51 with HERA: I. Radial averages of CO, HI, and radio continuum
• W43: the closest molecular complex of the Galactic Bar?
• A simple and accurate approximation for the Q stability parameter in multi-component and realistically thick discs
• Instabilities of Spiral Shocks I: Onset of Wiggle Instability and its Mechanism
• Global Modeling of Spur Formation in Spiral Galaxies
• The frequency and nature of `cloud-cloud collisions' in galaxies
• Accretion-Driven Turbulence and the Transition to Global Instability in Young Galaxy Disks
• Cloud-cloud collision as a trigger of the high-mass star formation; a molecular line study in RCW120
• Spurs and feathering in spiral galaxies
• Gravitational Instabilities in Two-Component Galaxy Disks with Gas Dissipation
• Scaling Relations of Star-Forming Regions: from kpc-size clumps to HII regions
• Non-linear violent disc instability with high Toomre's Q in high-redshift clumpy disc galaxies
• ATLASGAL -- A Galaxy-wide sample of dense filamentary structures
• The Formation of Molecular Clouds
• Evolution of violent gravitational disc instability in galaxies: Late stabilization by transition from gas to stellar dominance
• DYNAMO-HST Survey: Clumps in Nearby Massive Turbulent Disks and the Effects of Clump Clustering on Kiloparsec Scale Measurements of Clumps
• The Skeleton of the Milky Way
• Gravitational contraction versus Supernova driving and the origin of the velocity dispersion-size relation in molecular clouds
• A High Resolution Study of the HI-H2 Transition across the Perseus Molecular Cloud
• ALMA maps the Star-Forming Regions in a Dense Gas Disk at z~3
• Chain Galaxies in the Tadpole ACS Field
• A Toomre-like stability criterion for the clumpy and turbulent interstellar medium
• Mass Transport and Turbulence in Gravitationally Unstable Disk Galaxies II: The Effects of Star Formation Feedback
• On the self-regulation of intense star-formation in galaxies at z=1-3
• Evidence For Cloud-Cloud Collision and Parsec-Scale Stellar Feedback Within the L1641-N Region
• A Census of Large-Scale ($\ge$ 10 pc), Velocity-Coherent, Dense Filaments in the Northern Galactic Plane: Automated Identification Using Minimum Spanning Tree
• Clumpy galaxies at z~0.6: kinematics, stability, and comparison with analogs at other redshifts
• Giant molecular filaments in the Milky Way II: The fourth Galactic quadrant
• Was a cloud-cloud collision the trigger of the recent star formation in Serpens?
• A 500 pc filamentary gas wisp in the disk of the Milky Way
• Clusters of Small Clumps Can Explain The Peculiar Properties of Giant Clumps in High-Redshift Galaxies
• What drives gravitational instability in nearby star-forming spirals? The impact of CO and HI velocity dispersions
• Connecting Clump Sizes in Turbulent Disk Galaxies to Instability Theory
• The Interstellar Medium and star formation on kpc size scales
• Structure Formation in Gas-Rich Galactic Discs with Finite Thickness: From Discs to Rings
• Extreme gas fractions in clumpy, turbulent disk galaxies at z~0.1
• L1188: a promising candidate of cloud-cloud collision triggering the formation of the low- and intermediate-mass stars
• HI-to-H2 Transition Layers in the Star-Forming Region W43
• A complete 12CO 2--1 map of M51 with HERA: II. Total gas surface densities and gravitational stability
• Turbulent viscosity in clumpy accretion disks. Application to the Galaxy
• Chain Galaxies are Edge-On Low Surface Brightness Galaxies
• Clumpy high-z galaxies as a testbed for feedback-regulated galaxy formation
• Molecular cloud regulated star formation in galaxies
• Criteria for gravitational instability and quasi-isolated gravitational collapse in turbulent medium
• Revealing a spiral-shaped molecular cloud in our galaxy - Cloud fragmentation under rotation and gravity
• Interpreting observations of edge-on gravitationally unstable accretion flows
• Molecular Clouds: Internal Properties, Turbulence, Star Formation and Feedback

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• Kinematics of the molecular interstellar medium probed by Gaia: steep velocity dispersion-size relation, isotropic turbulence, and location-dependent energy dissipation
• GMC Collisions as Triggers of Star Formation. VI. Collision-Induced Turbulence
• WISDOM Project XII. Clump properties and turbulence regulated by clump-clump collisions in the dwarf galaxy NGC404
• Coupling local to global star formation in spiral galaxies: the effect of differential rotation
• A mean density of $112M_{\odot }\mathrm{p}{\mathrm{c}}^{-3}$ for Central Molecular Zone clumps -- Evidences for shear-enabled pressure equilibrium in the Galactic Center
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