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We studied the H$_2$ column density probability distribution function (N-PDF) based on molecular emission lines using the Nobeyama 45-m Cygnus X CO survey data. Using the DENDROGRAM and SCIMES algorithms, we identified 124 molecular clouds…

We show that the inter-cloud Larson scaling relation between mean volume density and size $\rho\propto R^{-1}$, which in turn implies that mass $M\propto R^2$, or that the column density $N$ is constant, is an artifact of the observational…

Astrophysics of Galaxies · Physics 2015-06-11 Ballesteros-Paredes , J. , D'Alessio , P. , Hartmann , L. W.

The density distribution within molecular clouds offers critical insights into their underlying physical processes, which are essential for understanding star formation. As a statistical measure of column density on the cloud scale, the…

Astrophysics of Galaxies · Physics 2026-01-12 Yuchen Xing , Keping Qiu

We have obtained column density maps for an unbiased sample of 120 molecular clouds in the third quadrant of the Milky Way mid-plane (b$\le |5|^{\circ}$) within the galactic longitude range from 195$^{\circ}$ to 225$^{\circ}$, using the…

Astrophysics of Galaxies · Physics 2022-08-31 Yuehui Ma , Hongchi Wang , Miaomiao Zhang , Chen Wang , Shaobo Zhang , Yao Liu , Chong Li , Yuqing Zheng , Lixia Yuan , Ji Yang

The formation of stars is inextricably linked to the structure of their parental molecular clouds. Here we take a number of nearby giant molecular clouds (GMCs) and analyse their column density and mass distributions. This investigation is…

Astrophysics of Galaxies · Physics 2015-05-18 D. Froebrich , J. Rowles

Structures in molecular ISM are observed to follow a power-law relation between the velocity dispersion and spatial size, known as Larson's first relation, which is often attributed to the turbulent nature of molecular ISM and imprints the…

Astrophysics of Galaxies · Physics 2024-10-22 Haoran Feng , Zhiwei Chen , Zhibo Jiang , Yuehui Ma , Yang Yang , Shuling Yu , Dongqing Ge , Wei Zhou , Fujun Du , Chen Wang , Shiyu Zhang , Yang Su , Ji Yang

We measure the mass and size of cloud fragments in several molecular clouds continuously over a wide range of spatial scales (0.05 < r / pc < 3). Based on the recently developed "dendrogram-technique", this characterizes dense cores as well…

Astrophysics of Galaxies · Physics 2015-05-18 Jens Kauffmann , Thushara Pillai , Rahul Shetty , Philip C. Myers , Alyssa A. Goodman

Volume and column density PDFs in molecular clouds are important diagnostics for understanding their general structure. We developed a novel approach to trace the cloud structure by varying the lower PDF cut-off and exploring a suggested…

Solar and Stellar Astrophysics · Physics 2013-08-02 Orlin Stanchev , Sava Donkov , Todor V. Veltchev , Rahul Shetty

We present CO(2-1) and $^{13}$CO(2-1) maps of the Cygnus-X molecular cloud complex using the 10m Heinrich Hertz Submillimeter Telescope (SMT). The maps cover the southern portion of the complex which is strongly impacted by the feedback…

Astrophysics of Galaxies · Physics 2023-12-22 Jonah C. Baade , Shuo Kong , John H. Bieging , Thomas Folkers

We introduce the concept of a class of equivalence of molecular clouds represented by an abstract spherically symmetric, isotropic object. This object is described by use of abstract scales in respect to a given mass density distribution.…

Astrophysics of Galaxies · Physics 2017-01-18 Sava Donkov , Todor V. Veltchev , Ralf S. Klessen

Column density (N) PDFs serve as a powerful tool to characterize the physical processes that influence the structure of molecular clouds. Star-forming clouds can best be characterized by lognormal PDFs for the lower N range and a power-law…

Different studies have reported a power-law mass-size relation $M \propto R^q$ for ensembles of molecular clouds. In the case of nearby clouds, the index of the power-law $q$ is close to 2. However, for clouds spread all over the Galaxy,…

Despite over 30 years of study, the mass-area relationship within and among clouds is still poorly understood both observationally and theoretically. Modern extinction datasets should have sufficient resolution and dynamic range to…

We study the mass-density relationship n ~ m^x in molecular cloud condensations (clumps), considering various equipartition relations between their gravitational, kinetic, internal and magnetic energies. Clumps are described statistically,…

Solar and Stellar Astrophysics · Physics 2015-05-20 Sava Donkov , Todor Veltchev , Ralf S. Klessen

In this Letter we investigate the shape of the probability distribution of column densities (PDF) in molecular clouds. Through the use of low-noise, extinction-calibrated \textit{Herschel}/\textit{Planck} emission data for eight molecular…

Solar and Stellar Astrophysics · Physics 2015-06-23 Marco Lombardi , João Alves , Charles J. Lada

Larson (1981) first noted a scaling relation between masses and sizes in molecular clouds that implies that these objects have approximately constant column densities. This original claim, based upon millimeter observations of carbon…

Astrophysics of Galaxies · Physics 2015-05-19 Marco Lombardi , Joao Alves , Charles J. Lada

We present results from a statistical study of clouds in two-dimensional numerical simulations of the interstellar medium. The clouds in the simulations exhibit a differential mass spectrum $dN(M)/dM \sim M^{-1.44 \pm 0.1}$ and a velocity…

Astrophysics · Physics 2009-10-28 E. Vazquez-Semadeni , J. Ballesteros-Paredes , L. F. Rodriguez

Both observational and theoretical research over the past decade has demonstrated that the probability distribution function (PDF) of the gas density in turbulent molecular clouds is a key ingredient for understanding star formation. It has…

Astrophysics of Galaxies · Physics 2018-11-28 Bastian Körtgen , Christoph Federrath , Robi Banerjee

The linewidth (sigma) - size (R) relationship has been extensively measured and analysed, in both the local ISM and in nearby normal galaxies. Generally, a power-law describes the relationship well with an index ranging from 0.2-0.6, now…

Astrophysics of Galaxies · Physics 2015-06-05 Rahul Shetty , Christopher N. Beaumont , Michael G. Burton , Brandon C. Kelly , Ralf S. Klessen

Describing how the properties of the interstellar medium combine across size-scales is crucial for understanding star formation scaling laws and connecting Galactic and extragalactic data of molecular clouds. We describe how the statistical…

Astrophysics of Galaxies · Physics 2021-09-15 Andri Spilker , Jouni Kainulainen , Jan Orkisz
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