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The velocity distribution of a fluidized dilute granular gas in the direction perpendicular to the gravitational field is investigated by means of Molecular Dynamics simulations. The results indicate that the velocity distribution can be…

Statistical Mechanics · Physics 2009-11-07 J. Javier Brey , M. J. Ruiz-Montero

It has been recently shown that molecular clouds do not exhibit a unique shape for the column density probability distribution function (Npdf). Instead, clouds without star formation seem to possess a lognormal distribution, while clouds…

I describe the scenario of molecular cloud (MC) evolution that has emerged over the past decade or so. MCs can start out as cold atomic clouds formed by compressive motions in the warm neutral medium (WNM) of galaxies. Such motions can be…

Astrophysics of Galaxies · Physics 2010-09-22 Enrique Vazquez-Semadeni

The evolution of molecular clouds in galactic centres is thought to differ from that in galactic discs due to a significant influence of the external gravitational potential. We present a set of numerical simulations of molecular clouds…

We discuss constraints on the rates of stirring and dissipation of MHD turbulence in molecular clouds. Recent MHD simulations suggest that turbulence in clouds decays rapidly, thus providing a significant source of energy input,…

Astrophysics · Physics 2009-11-06 Shantanu Basu , Chigurupati Murali

[Abridged] We present an analysis of the relation between the masses of cluster- and group-sized halos, extracted from $\Lambda$CDM cosmological N-body and hydrodynamic simulations, and their velocity dispersions, at different redshifts…

Cosmology and Nongalactic Astrophysics · Physics 2013-03-04 Emiliano Munari , Andrea Biviano , Stefano Borgani , Giuseppe Murante , Dunja Fabjan

We examine the physical parameters that affect the accumulation of gas in molecular clouds to high column densities where the formation of stars takes place. In particular, we analyze the dense gas mass fraction (DGMF) in a set of…

Astrophysics of Galaxies · Physics 2015-06-15 Jouni Kainulainen , Christoph Federrath , Thomas Henning

Supersonic turbulence is an essential element in understanding how structure within interstellar gas is created and shaped. In the context of star formation, many computational studies show that the mass spectrum of density and velocity…

Astrophysics of Galaxies · Physics 2014-03-05 Ralph E. Pudritz , N. K. -R. Kevlahan

Star clusters are known to be formed in turbulent molecular clouds. How turbulence is driven in molecular clouds and what effect this has on star formation is still unclear. We compare a simulation setup with turbulent driving everywhere in…

Astrophysics of Galaxies · Physics 2022-09-28 Jamie D. Smith , James E. Dale , Sarah E. Jaffa , Martin G. H. Krause

Evaporation of cloud droplets accelerates when turbulence mixes dry air into the cloud, affecting droplet-size distributions in atmospheric clouds, combustion sprays, and jets of exhaled droplets. The challenge is to model local…

Fluid Dynamics · Physics 2023-12-21 J. Fries , G. Sardina , G. Svensson , A. Pumir , B. Mehlig

We review the properties of turbulent molecular clouds (MCs), focusing on the physical processes that influence star formation (SF). MC formation appears to occur during large-scale compression of the diffuse ISM driven by supernovae,…

Astrophysics · Physics 2007-05-23 J. Ballesteros-Paredes , R. S. Klessen , M. -M. Mac Low , E. Vazquez-Semadeni

We present high resolution ($1024^3$) simulations of super-/hyper-sonic isothermal hydrodynamic turbulence inside an interstellar molecular cloud (resolving scales of typically 20 -- 100 AU), including a multi-disperse population of dust…

Astrophysics of Galaxies · Physics 2018-12-19 Lars Mattsson , Akshay Bhatnagar , Fred A. Gent , Beatriz Villarroel

This two-part review summarizes interstellar turbulence and its implications. The first part begins with diagnostics and energy sources. Turbulence theory is considered in detail, including the basic fluid equations, solenoidal and…

Astrophysics · Physics 2008-11-26 Bruce G. Elmegreen , John Scalo

Flows in natural bodies of fluid often become turbulent, with eddy-like motions dominated by inertial-vortex forces. Buoyancy, Coriolis, viscous, self-gravitational, electromagnetic, and other force constraints produce a complex phase space…

Astrophysics · Physics 2007-05-23 Carl H. Gibson

In this work, we investigate the properties of a population of cool clouds in simulated galaxy outflows. Using data from the CGOLS isolated galaxy simulations, we generate catalogues of $\sim 10^5$ clouds. We describe the impact of two…

Astrophysics of Galaxies · Physics 2024-10-16 Orlando Warren , Evan E. Schneider , S. Alwin Mao , Matthew W. Abruzzo

Understanding the dynamics of material objects advected by turbulent flows is a long standing question in fluid dynamics. In this perspective article we focus on the characterization of the statistical properties of non-interacting…

Fluid Dynamics · Physics 2024-03-18 Yaning Fan , Cheng Wang , Linfeng Jiang , Chao Sun , Enrico Calzavarini

(Abridged) The formation of molecular clouds (MCs) from the diffuse interstellar gas appears to be a necessary step for star formation, as young stars invariably occur within them. However, the mechanisms controlling the formation of MCs…

Astrophysics · Physics 2007-11-26 P. Hennebelle , M. -M. Mac Low , E. Vazquez-Semadeni

A fundamental property of molecular clouds is that they are turbulent, but how this turbulence is generated and maintained is unknown. One possibility is that stars forming within the cloud regenerate turbulence via their outflows, winds…

Solar and Stellar Astrophysics · Physics 2018-10-17 Stella S. R. Offner , Yue Liu

The fragmentation of gas to form stars in molecular clouds is intrinsically linked to the turbulence within them. These internal motions are set at the birth of the cloud and may vary with galactic environment and as the cloud evolves. In…

Astrophysics of Galaxies · Physics 2024-07-29 Jiten Dhandha , Zoe Faes , Rowan J. Smith

Giant molecular clouds contain supersonic turbulence and simulations of magnetohydrodynamic turbulence show that these supersonic motions decay in roughly a crossing time, which is less than the estimated lifetimes of molecular clouds. Such…

Astrophysics of Galaxies · Physics 2012-07-13 A. Pon , D. Johnstone , M. J. Kaufman