On the Spatial Distribution of ${}^{13}$CO Structures within ${}^{12}$CO Molecular Clouds

Abstract

We look into the 2851 ${}^{12}$CO molecular clouds harboring ${}^{13}$CO structures to reveal the distribution of the projected angular separations and radial velocity separations between their internal ${}^{13}$CO structures. The projected angular separations are determined using the minimal spanning tree algorithm. We find that $\sim$ 50$\%$ of the angular separations fall in a narrow range of $\sim$ 3 - 7 arcmin with a median of $\sim$ 5 arcmin, and the corresponding radial velocity separations mainly range from $\sim$ 0.3 km s${}^{-1}$ to 2.5 km s${}^{-1}$. The mean and standard deviation of the angular separations of the internal ${}^{13}$CO structures within ${}^{12}$CO clouds appear to be universal, independent of the ${}^{12}$CO cloud angular areas and the counts of their internal ${}^{13}$CO structures. We also reveal a scaling relation between the ${}^{12}$CO cloud angular area and its harbored ${}^{13}$CO structure count. These results suggest there is a preferred angular separation between ${}^{13}$CO structures in these ${}^{12}$CO clouds, considering the distance effects. According to that, we propose an alternative picture for the assembly and destruction of molecular clouds: there is a fundamental separation for the internal structures of molecular clouds, the build-up and destruction of molecular clouds proceeds under this fundamental unit.

arXiv comment14 pages, 12 figures, accepted for publication in ApJ

References in corpus (58)

• SciPy 1.0--Fundamental Algorithms for Scientific Computing in Python
• Astropy: A Community Python Package for Astronomy
• Binary companions of evolved stars in APOGEE DR14: Search method and catalog of ~5,000 companions
• From filamentary clouds to prestellar cores to the stellar IMF: Initial highlights from the Herschel Gould Belt survey
• Clouds, filaments and protostars: the Herschel Hi-GAL Milky Way
• Characterizing interstellar filaments with Herschel in IC5146
• Rapid Formation of Molecular Clouds and Stars in the Solar Neighborhood
• The Universality of the Stellar IMF
• Filamentary structure of star-forming complexes
• The Universality of Turbulence in Galactic Molecular Clouds
• Cores, filaments, and bundles: hierarchical core formation in the L1495/B213 Taurus region
• Gravitational Collapse in Turbulent Molecular Clouds. I. Gasdynamical Turbulence
• Bias-free Measurement of Giant Molecular Cloud Properties
• A Parallax-based Distance Estimator for Spiral Arm Sources
• Star Formation in Disk Galaxies. I. Formation and Evolution of Giant Molecular Clouds via Gravitational Instability and Cloud Collisions
• Dawes Review 4: Spiral Structures in Disc Galaxies
• Molecular cloud evolution. I. Molecular cloud and thin CNM sheet formation
• An ALMA study of the Orion Integral Filament: I. Evidence for narrow fibers in a massive cloud
• Clouds as Turbulent Density Fluctuations. Implications for pressure confinement and spectral line data interpretation
• On the Density Probability Function of Galactic Gas. I. Numerical Simulations and the Significance of the Polytropic Index
• The Birth of Molecular Clouds: Formation of Atomic Precursors in Colliding Flows
• Molecular Cloud Formation Behind Shock Waves
• The Milky Way Imaging Scroll Painting (MWISP): Project Details and Initial Results from the Galactic Longitude of 25.8deg to 49.7deg
• The properties of the ISM in disc galaxies with stellar feedback
• A Holistic Scenario of Turbulent Molecular Cloud Evolution and Control of the Star Formation Efficiency. First Tests
• Chains of dense cores in the Taurus L1495/B213 complex
• Molecular Clouds Toward the Super Star Cluster NGC3603; Possible Evidence for a Cloud-Cloud Collision in Triggering the Cluster Formation
• A Turbulent Model for the Interstellar Medium. II. Magnetic Fields and Rotation
• The identification of filaments on far infrared and submillimiter images. Morphology, physical conditions and relation with star formation of filamentary structure
• How long does it take to form a molecular cloud?
• The frequency and nature of `cloud-cloud collisions' in galaxies
• Properties of the dense core population in Orion B as seen by the Herschel Gould Belt survey
• The two molecular clouds in RCW 38; evidence for formation of the youngest super star cluster in the Milky Way triggered by cloud-cloud collision
• Filamentary fragmentation in a turbulent medium
• Two Mass Distributions in the L 1641 Molecular Clouds: The Herschel connection of Dense Cores and Filaments in Orion A
• Characterizing filaments in regions of high-mass star formation: High-resolution submilimeter imaging of the massive star-forming complex NGC 6334 with ArTéMiS
• Spatial Distributions of Young Stars
• Intermittency of interstellar turbulence: extreme velocity-shears and CO emission on milliparsec scale
• Resolving the fragmentation of high line-mass filaments with ALMA: the integral shaped filament in Orion A
• Cloud and Star Formation in Disk Galaxy Models with Feedback
• A Census of Large-Scale ($\ge$ 10 pc), Velocity-Coherent, Dense Filaments in the Northern Galactic Plane: Automated Identification Using Minimum Spanning Tree
• From diffuse gas to dense molecular cloud cores
• The Spatial Distribution of the Young Stellar Clusters in the Star Forming Galaxy NGC 628
• A 500 pc filamentary gas wisp in the disk of the Milky Way
• SEDIGISM: The kinematics of ATLASGAL filaments
• Distances and statistics of local molecular clouds in the first Galactic quadrant
• L1188: a promising candidate of cloud-cloud collision triggering the formation of the low- and intermediate-mass stars
• Dynamical cloud formation traced by atomic and molecular gas
• Strong dependence of the physical properties of cores on spatial resolution in observations and simulations
• Edge collapse and subsequent longitudinal accretion in Filament S242
• A Morphological Classification of 18190 Molecular Clouds Identified in ${}^{12}$CO Data from the MWISP Survey
• Molecular Clouds in the Second Quadrant of the Milky Way Mid-plane from l$=$104$.{}^{\circ }$75 to l=119$.{}^{\circ }$75 and b=$-$5$.{}^{\circ }$25 to b=5$.{}^{\circ }$25
• Distances to molecular clouds in the second Galactic quadrant
• Gas Column Density Distribution of Molecular Clouds in the Third Quadrant of the Milky Way
• Improved Measurements of Molecular Cloud Distances Based on Global Search
• A wide-field CO survey towards the California Molecular Filament
• Dependence of Molecular Cloud Samples on Angular Resolution, Sensitivity, and Algorithms
• Molecular Gas Structures traced by ${}^{13}$CO Emission in the 18,190 ${}^{12}$CO Molecular Clouds from the MWISP Survey

Cited by in corpus (2)

• On the Flux-Intensity Relation of Molecular Clouds
• Molecular Clouds in the Galactic Plane from $l$ = [59.75${}^{\circ }$, 74.75${}^{\circ }$] and $b$ = [$-$5.25${}^{\circ }$, +5.25${}^{\circ }$]