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We conduct numerical experiments to determine the density probability distribution function (PDF) produced in supersonic, isothermal, self-gravitating turbulence of the sort that is ubiquitous in star-forming molecular clouds. Our…

Astrophysics of Galaxies · Physics 2021-08-10 Shivan Khullar , Christoph Federrath , Mark R. Krumholz , Christopher D. Matzner

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 a general framework to treat the evolution of one-point probability distribution function (PDF) for cosmic density $\delta$ and velocity-divergence fields $\theta$. In particular, we derive an evolution equation for the one-point…

Astrophysics · Physics 2009-11-07 Yasuhiro Ohta , Issha Kayo , Atsushi Taruya

We introduce a theory for the development of a transitional column density $\Sigma_{\rm TP}$ between the lognormal and the power-law forms of the probability distribution function (PDF) in a molecular cloud. Our turbulent…

Solar and Stellar Astrophysics · Physics 2019-08-14 Sayantan Auddy , Shantanu Basu , Takahiro Kudoh

There has been overwhelming evidence that coherent structures play a critical role in determining the overall transport in a variety of systems. We compute the probability distribution function (PDF) tails of momentum flux and heat flux in…

Plasma Physics · Physics 2009-11-13 Johan Anderson , Eun-jin Kim

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…

The time evolution of the probability density function (PDF) of the mass density is formulated and solved for systems in free-fall using a simple appoximate function for the collapse of a sphere. We demonstrate that a pressure-free collapse…

Astrophysics of Galaxies · Physics 2015-06-17 Philipp Girichidis , Lukas Konstandin , Anthony P. Whitworth , Ralf S. Klessen

Under ideal conditions, the probability density function (PDF) of a random variable, such as a sensor measurement, would be well known and amenable to computation and communication tasks. However, this is often not the case, so the user…

Statistics Theory · Mathematics 2022-07-29 Shane Lubold , Clark N. Taylor

The probability density function (PDF) of velocity fluctuations is studied experimentally for grid turbulence in a systematical manner. At small distances from the grid, where the turbulence is still developing, the PDF is sub-Gaussian. At…

Fluid Dynamics · Physics 2009-11-07 H. Mouri , M. Takaoka , A. Hori , Y. Kawashima

We present probability distribution functions (PDFs) of the surface densities of ionized and neutral gas in the nearby spiral galaxies M31 and M51, as well as of dust emission and extinction Av in M31. The PDFs are close to lognormal and…

Astrophysics of Galaxies · Physics 2015-06-23 Elly M. Berkhuijsen , Andrew Fletcher

The properties of the probability distribution function of the cosmological continuous density field are studied. We present further developments and compare dynamically motivated methods to derive the PDF. One of them is based on the…

Astrophysics · Physics 2009-10-22 F. Bernardeau , L. Kofman

We have conducted a large-field simultaneous survey of $^{12}$CO, $^{13}$CO, and C$^{18}$O $J=1-0$ emission toward the Orion A giant molecular cloud (GMC) with a sky coverage of $\sim$ 4.4 deg$^2$ using the PMO-13.7 m millimeter-wavelength…

Astrophysics of Galaxies · Physics 2020-05-06 Yuehui Ma , Hongchi Wang , Chong Li , Ji Yang

We present a simple model based on the dark halo approach which provides a useful way to understand key points determining the shape of the non-Gaussian tails of the dark matter one-point probability distribution function(PDF). In…

Astrophysics · Physics 2009-11-07 Atsushi Taruya , Takashi Hamana , Issha Kayo

The evolution of probability distribution functions (PDFs) of continuous density, velocity and velocity derivatives ( deformation tensor) fields in the theory of cosmological gravitational instability are considered. We show that in the…

Astrophysics · Physics 2007-05-23 Lev Kofman

The probability density function (PDF) of a global measure in a large class of highly correlated systems has been suggested to be of the same functional form. Here, we identify the analytical form of the PDF of one such measure, the order…

This letter provides the first prediction of the probability density function (PDF) of flux $R$ in plasma sheath sheath region in magnetic fusion devices which is characterized by dynamical equations with exponential non-linearities. By…

Plasma Physics · Physics 2015-05-13 Johan Anderson , Eun-jin Kim

We calculate the one-point probability distribution function (PDF) for cosmic density in non-linear regime of the gravitational evolution. Under the local approximation that the evolution of cosmic fluid fields can be characterized by the…

Astrophysics · Physics 2009-11-10 Yasuhiro Ohta , Issha Kayo , Atsushi Taruya

Turbulence is essential for understanding the structure and dynamics of molecular clouds and star-forming regions. There is a need for adequate tools to describe and characterize the properties of turbulent flows. One-point probability…

Astrophysics · Physics 2008-11-26 Ralf S. Klessen

Numerical simulations of the collapse and spreading of granular columns onto an horizontal plane using the Contact Dynamics method are presented. The final shape of the deposit seems to depend only on the aspect ratio $a$ of the columns;…

Geophysics · Physics 2009-11-11 L. Staron , E. J. Hinch