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.

14 pages, 12 figures, accepted for publication in ApJ

References in corpus (27)

• Filamentary structure of star-forming complexes
• Bias-free Measurement of Giant Molecular Cloud Properties
• 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
• The Birth of Molecular Clouds: Formation of Atomic Precursors in Colliding Flows
• The Milky Way Imaging Scroll Painting (MWISP): Project Details and Initial Results from the Galactic Longitude of 25.8deg to 49.7deg
• Chains of dense cores in the Taurus L1495/B213 complex
• The identification of filaments on far infrared and submillimiter images. Morphology, physical conditions and relation with star formation of filamentary structure
• 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
• Spatial Distributions of Young Stars
• 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
• 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

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