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We present a systematic analysis of the velocity structure functions (VSFs) of 167 molecular clouds with angular sizes greater than $\sim$176 arcmin$^2$ in three sectors of the Galactic mid-plane. We calculated the 1st- to 3rd-order VSFs…

We investigate physical properties of molecular clouds in disc galaxies with different morphology: a galaxy without prominent structure, a spiral barred galaxy and a galaxy with flocculent structure. Our $N$-body/hydrodynamical simulations…

Astrophysics of Galaxies · Physics 2016-03-02 S. A. Khoperskov , E. O. Vasiliev , D. A. Ladeyschikov , A. M. Sobolev , A. V. Khoperskov

We analyse the distribution of CO brightness temperature and integrated intensity in M51 at ~40 pc resolution using new CO data from the Plateau de Bure Arcsecond Whirlpool Survey (PAWS). We present probability distribution functions (PDFs)…

Observations of magnetic field strengths imply that molecular cloud fragments are individually close to being in a magnetically critical state, even though both magnetic field and column density measurements range over two orders of…

Astrophysics · Physics 2007-05-23 Shantanu Basu

We measure the matter probability distribution function (PDF) via counts in cells in a volume limited subsample of the Sloan Digital Sky Survey Luminous Red Galaxy Catalog on scales from $30 h^{-1}$Mpc to $150 h^{-1}$Mpc and estimate the…

Cosmology and Nongalactic Astrophysics · Physics 2010-12-16 Péter Pápai , István Szapudi

The magnetic field strength in molecular clouds is a fundamental quantity for theories of star formation. It is estimated by Zeeman splitting measurements in a few dense molecular cores, but its volume--averaged value within large molecular…

Astrophysics · Physics 2009-11-10 Paolo Padoan , Raul Jimenez , Mika Juvela , Aake Nordlund

(Abridged) We derive an analytical formula which provides estimates on multiscale gravitational energy distribution using the observed surface density PDF. Our analytical formalism also enables one to convert the observed column density PDF…

Solar and Stellar Astrophysics · Physics 2016-07-07 Guang-Xing Li , Andreas Burkert

The question of the shape of the density PDF for supersonic turbulence is addressed, using both analytical and numerical methods. For isothermal supersonic turbulence, the PDF is Log-Normal, with a width that scales approximately linearly…

Astrophysics · Physics 2007-05-23 AAke Nordlund , Paolo Padoan

We define the molecular cloud properties of the Milky Way first quadrant using data from the JCMT CO(3-2) High Resolution Survey. We apply the Spectral Clustering for Interstellar Molecular Emission Segmentation (SCIMES) algorithm to…

We quantitatively study the probability distribution function (PDF) of cosmological nonlinear density fluctuations from N-body simulations with Gaussian initial condition. In particular, we examine the validity and limitations of one-point…

Astrophysics · Physics 2009-11-06 Issha Kayo , Atsushi Taruya , Yasushi Suto

We determine that the sizes of bursts in mean-square current density in a reduced magnetohydrodynamic (RMHD)simulation follow power-law probability density function (PDF). The PDFs for burst durations and waiting time between bursts are…

Astrophysics · Physics 2009-10-31 N. W. Watkins , S. Oughton , M. P. Freeman

The emergence and development of a power-law tail (PLT) at the high-density end of the observed column-density distribution is thought to be indicative for advanced evolution of star-forming molecular clouds. As shown from many numerical…

Astrophysics of Galaxies · Physics 2021-10-04 L. Marinkova , T. Veltchev , Ph. Girichidis , S. Donkov

Theoretical and observational investigations have indicated that the abundance of carbon monoxide (CO) is very sensitive to intrinsic properties of the gaseous medium, such as density, metallicity, and the background UV field. In order to…

Astrophysics of Galaxies · Physics 2015-05-20 Rahul Shetty , Simon C. Glover , Cornelis P. Dullemond , Ralf S. Klessen

Compressive isothermal turbulence is known to have a near lognormal density probability distribution function (PDF) with a width that scales with the sonic Mach number and nature of the turbulent driving (solenoidal vs compressive).…

Astrophysics of Galaxies · Physics 2019-11-06 Philip Mocz , Blakesley Burkhart

We examine the effects of self-gravity and magnetic fields on supersonic turbulence in isothermal molecular clouds with high resolution simulations and adaptive mesh refinement. These simulations use large root grids (512^3) to capture…

Solar and Stellar Astrophysics · Physics 2015-06-04 David Collins , Alexei G. Kritsuk , Paolo Padoan , Hui Li , Hao Xu , Sergey D. Ustyugov , Michael L. Norman

Mathematical models based on probability density functions (PDF) have been extensively used in hydrology and subsurface flow problems, to describe the uncertainty in porous media properties (e.g., permeability modelled as random field).…

Fluid Dynamics · Physics 2020-06-01 Matteo Icardi , Marco Dentz

While second and higher order correlations of the light distribution have received extensive study, the lowest order probability distribution function (PDF) -- the probability that a unit volume of space will emit a given amount of light --…

Astrophysics · Physics 2009-11-07 Jeremiah P. Ostriker , Kentaro Nagamine , Renyue Cen , Masataka Fukugita

We investigate velocity probability distribution functions (PDF) of sheared hard-sphere suspensions. As observed in our Stokes flow simulations and explained by our single-particle theory, these PDFs can show pronounced deviations from a…

Soft Condensed Matter · Physics 2008-07-24 Jens Harting , Hans J. Herrmann , Eli Ben-Naim

Far-infrared molecular emission is an important tool used to understand the excitation mechanisms of the gas in the inter-stellar medium of star-forming galaxies. In the present work, we model the emission from rotational transitions with…

Astrophysics of Galaxies · Physics 2016-11-23 M. V. Kazandjian , I. Pelupessy , R. Meijerink , F. P. Israel , C. M. Coppola , M. J. F. Rosenberg , M. Spaans

We derive a first order linear differential equation describing the shape of the probability density function of magnetic field strengths in the quiet Sun (PDF). The modeling is very schematic. It considers convective motions which…

Astrophysics · Physics 2008-11-26 J. Sanchez Almeida