Solenoidal turbulent modes and star formation efficiency in Galactic-plane molecular clouds

Abstract

It is speculated that the high star-formation efficiency observed in spiral-arm molecular clouds is linked to the prevalence of compressive (curl-free) turbulent modes, while the shear-driven solenoidal (divergence-free) modes appear to be the main cause of the low star-formation efficiency that characterises clouds in the Central Molecular Zone. Similarly, analysis of the Orion B molecular cloud has confirmed that, although turbulent modes vary locally and at different scales within the cloud, the dominant solenoidal turbulence is compatible with its low star formation rate. This evidence points to inter-and intra-cloud fluctuations of the solenoidal modes being an agent for the variability of star formation efficiency. We present a quantitative estimation of the relative fractions of momentum density in the solenoidal modes of turbulence in a large sample of plane molecular clouds in the \ce{^{13}CO}/\ce{C^{18}O} ($J=3\to 2$) Heterodyne Inner Milky Way Plane Survey (CHIMPS). We find a negative correlation between the solenoidal fraction and star-formation efficiency. This feature is consistent with the hypothesis that solenoidal modes prevent or slow down the collapse of dense cores. In addition, the relative power in the solenoidal modes of turbulence (solenoidal fraction) appears to be higher in the Inner Galaxy declining with a shallow gradient with increasing Galactocentric distance. Outside the Inner Galaxy, the slowly, monotonically declining values suggest that the solenoidal fraction is unaffected by the spiral arms.

arXiv comment16 pages, 14 figures

References in corpus (79)

• Astropy: A Community Python Package for Astronomy
• The Astropy Project: Building an inclusive, open-science project and status of the v2.0 core package
• The Global Schmidt Law in Star Forming Galaxies
• Embedded Clusters in Molecular Clouds
• Theory of Star Formation
• The Star Formation Efficiency in Nearby Galaxies: Measuring Where Gas Forms Stars Effectively
• Control of star formation by supersonic turbulence
• THINGS: The HI Nearby Galaxy Survey
• Trigonometric Parallaxes of High Mass Star Forming Regions: the Structure and Kinematics of the Milky Way
• SINGS: The SIRTF Nearby Galaxies Survey
• Interstellar Turbulence I: Observations and Processes
• The Star Formation Rate and Dense Molecular Gas in Galaxies
• The GALEX Ultraviolet Atlas of Nearby Galaxies
• HERACLES: The HERA CO-Line Extragalactic Survey
• The Density Probability Distribution in Compressible Isothermal Turbulence: Solenoidal versus Compressive Forcing
• The Star Formation Law in Atomic and Molecular Gas
• ATLASGAL --- properties of a complete sample of Galactic clumps
• Physical Properties and Galactic Distribution of Molecular Clouds identified in the Galactic Ring Survey
• Variations in the Galactic star formation rate and density thresholds for star formation
• The maximum stellar mass, star-cluster formation and composite stellar populations
• Interstellar Turbulence II: Implications and Effects
• Star Formation Rates in Molecular Clouds and the Nature of the Extragalactic Scaling Relations
• Dawes Review 4: Spiral Structures in Disc Galaxies
• Protostellar Turbulence Driven by Collimated Outflows
• Mach Number Dependence of Turbulent Magnetic Field Amplification: Solenoidal versus Compressive Flows
• Star Formation Relations in Nearby Molecular Clouds
• HARP/ACSIS: A submillimetre spectral imaging system on the James Clerk Maxwell Telescope
• An uncertainty principle for star formation. I. Why galactic star formation relations break down below a certain spatial scale
• The link between turbulence, magnetic fields, filaments, and star formation in the Central Molecular Zone cloud G0.253+0.016
• The anatomy of the Orion B Giant Molecular Cloud: A local template for studies of nearby galaxies
• Properties of Hi-GAL clumps in the inner Galaxy]{The Hi-GAL compact source catalogue. I. The physical properties of the clumps in the inner Galaxy ($-71.0^{\circ }<\ell <67.0^{\circ }$)
• Gas Kinematics on GMC scales in M51 with PAWS: cloud stabilization through dynamical pressure
• The properties of the ISM in disc galaxies with stellar feedback
• ATLASGAL --- Environments of 6.7\,GHz methanol masers
• The RMS Survey: Critical Tests of Accretion Models for the Formation of Massive Stars
• Molecular Cloud Evolution IV: Magnetic Fields, Ambipolar Diffusion, and the Star Formation Efficiency
• The Luminosity Functions and Timescales of MYSOs and Compact HII regions
• Understanding the H2/HI Ratio in Galaxies
• CHIMPS: the ${}^{13}$CO/C${}^{18}$O (J=3-2) Heterodyne Inner Milky Way Plane Survey
• Graph-based interpretation of the Molecular Interstellar Medium Segmentation
• The Galactic Center Cloud G0.253+0.016: A Massive Dense Cloud with low Star Formation Potential
• On the Similarity between Cluster and Galactic Stellar Initial Mass Functions
• Bar-driven evolution and quenching of spiral galaxies in cosmological simulations
• Dense Gas Tracers and Star Formation Laws in Active Galaxies: APEX Survey of HCN J=4-3, HCO+ J=4-3, and CS J=7-6
• Turbulence and star formation efficiency in molecular clouds: solenoidal versus compressive motions in Orion B
• A Model for the Onset of Self-gravitation and Star Formation in Molecular Gas Governed by Galactic Forces: I. Cloud-scale Gas Motions
• A method for reconstructing the variance of a 3D physical field from 2D observations: Application to turbulence in the ISM
• Molecular clouds and clumps in the Boston University-Five College Radio Astronomy Observatory Galactic Ring Survey
• Star formation in Galactic spiral arms and the inter-arm regions
• Aspect Ratio Dependence of the Free-Fall Time for Non-Spherical Symmetries
• The dynamical evolution of molecular clouds near the Galactic Centre - II. Spatial structure and kinematics of simulated clouds
• Fragmentation of Shocked Flows: Gravity, Turbulence and Cooling
• A general theory for the lifetimes of giant molecular clouds under the influence of galactic dynamics
• The integrated properties of the molecular clouds from the JCMT CO(3-2) High Resolution Survey
• Star formation towards the Scutum tangent region and the effects of Galactic environment
• The H alpha Galaxy Survey VII. The spatial distribution of star formation within disks and bulges
• The SILCC project - V. The impact of magnetic fields on the chemistry and the formation of molecular clouds
• The Free-Fall time of finite Sheets and Filaments
• The dynamics and star-forming potential of the massive Galactic centre cloud G0.253+0.016
• The Effect of Spiral Arms on Star Formation in the Galaxy
• The JCMT Plane Survey: early results from the l = 30 degree field
• Stellar population constraints on the ages of galactic bars
• CHIMPS: Physical properties of molecular clumps across the inner Galaxy
• The JCMT Plane Survey: First complete data release - emission maps and compact source catalogue
• Trans-Alfvenic Motions in the Taurus Molecular Cloud
• Impact of Winds from Intermediate-Mass Stars on Molecular Cloud Structure and Turbulence
• Star formation scales and efficiency in Galactic spiral arms
• The JCMT Gould Belt Survey: A First Look at Dense Cores in Orion B
• CHIMPS2: Survey description and ${}^{12}$CO emission in the Galactic Centre
• The prevalence of star formation as a function of Galactocentric radius
• A model for the onset of self-gravitation and star formation in molecular gas governed by galactic forces: II. the bottleneck to collapse set by cloud-environment decoupling
• The Lesser Role of Shear in Star Formation: Insight from the Galactic Ring Survey
• TurbuStat: Turbulence Statistics in Python
• Three-Dimensional Distribution of the ISM in the Milky Way Galaxy: IV. 3D Molecular Fraction and Galactic-Scale HI-to-H${}_2$ Transition
• Multifractal Analysis of the Interstellar Medium. First application to Hi-GAL Observations
• The role of spiral arms in Milky Way star formation
• An Observational Method to Measure the Relative Fractions of Solenoidal and Compressible Modes in Interstellar Clouds
• Kinematics of the molecular interstellar medium probed by Gaia: steep velocity dispersion-size relation, isotropic turbulence, and location-dependent energy dissipation
• Characteristic scale of star formation. I. Clump formation efficiency on local scales

Cited by in corpus (5)

• Wide binary stars formed in the turbulent interstellar medium
• Kinematics of Galactic Centre clouds shaped by shear-seeded solenoidal turbulence
• The influence of the cloud virial parameter on the initial mass function
• Assessing the accuracy of the star formation rate measurements by direct star count in molecular clouds
• Decaying turbulence in molecular clouds: how does it affect filament networks and star formation?