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Author: Jonathan J. Carroll-Nellenback Publisher: ISBN: Category : Languages : en Pages : 124
Book Description
"Star formation occurs within complex assemblies of cold dense matter known as molecular clouds. The dynamics of these clouds involve a wide variety of physical processes over a wide range in length scales, making numerical modeling of these clouds a challenging and interesting problem. On the largest scales (10-100 parsec) there is a constant battle between forces acting to support or unbind the cloud (stellar feedback from super-novae and HII regions, magnetic fields, turbulence, and shear), and those attempting to compress the cloud (thermal and/or ram pressure from the interstellar medium (ISM) and gravity). On smaller scales the same turbulent motions that support the cloud as a whole can produce dense filamentary regions within the cloud that can undergo local collapse. On intermediate scales (1 pc), feedback in the form of winds and outflows can disrupt density structures and provide turbulent energy to reduce the rate of star formation. The large dynamical range requires use of sophisticated codes such as AstroBEAR. The high degree of resolution required as well as the increase in the sheer number of central processing units (CPUs) available to perform calculations requires codes that achieve new levels of efficient parallelization and memory management. We have employed new techniques to achieve both of these goals in our modeling of various aspects of turbulence in molecular clouds including turbulence driven by stellar feedback within the cloud, turbulence driven externally, and turbulence driven by the interaction of inhomogeneous streams of gas within the ISM"--Page iv.
Author: Jonathan J. Carroll-Nellenback Publisher: ISBN: Category : Languages : en Pages : 124
Book Description
"Star formation occurs within complex assemblies of cold dense matter known as molecular clouds. The dynamics of these clouds involve a wide variety of physical processes over a wide range in length scales, making numerical modeling of these clouds a challenging and interesting problem. On the largest scales (10-100 parsec) there is a constant battle between forces acting to support or unbind the cloud (stellar feedback from super-novae and HII regions, magnetic fields, turbulence, and shear), and those attempting to compress the cloud (thermal and/or ram pressure from the interstellar medium (ISM) and gravity). On smaller scales the same turbulent motions that support the cloud as a whole can produce dense filamentary regions within the cloud that can undergo local collapse. On intermediate scales (1 pc), feedback in the form of winds and outflows can disrupt density structures and provide turbulent energy to reduce the rate of star formation. The large dynamical range requires use of sophisticated codes such as AstroBEAR. The high degree of resolution required as well as the increase in the sheer number of central processing units (CPUs) available to perform calculations requires codes that achieve new levels of efficient parallelization and memory management. We have employed new techniques to achieve both of these goals in our modeling of various aspects of turbulence in molecular clouds including turbulence driven by stellar feedback within the cloud, turbulence driven externally, and turbulence driven by the interaction of inhomogeneous streams of gas within the ISM"--Page iv.
Book Description
This timely volume presents a series of review articles covering every aspect of interstellar turbulence--from accretion disks, molecular clouds, atomic and ionized media, through to spiral galaxies - based on a major international conference held in Mexico City.With advances in observational techniques and the development of more efficient computer codes and faster computers, research in this area has made spectacular progress in recent years. This book provides a comprehensive overview of the most important developments in observing and modelling turbulent flows in the cosmos. It provides graduate student and researchers with a state-of-the-art summary of observational, theoretical and computational research in interstellar turbulence.
Author: Christoph Federrath Publisher: LAP Lambert Academic Publishing ISBN: 9783838364933 Category : Languages : en Pages : 212
Book Description
Turbulent compression is considered a key process in molecular cloud and star formation. Over the last years, interstellar turbulence has thus been studied both in direct observations and in computer simulations. Apart from Kolmogorov s phenomenological model of incompressible turbulence, however, a complete theory of highly compressible turbulence remains elusive. The goal of this work is to improve our understanding of the role of interstellar turbulence for star formation. In particular, the two limiting cases of turbulence energy injection are investigated in hydrodynamical computer simulations: solenoidal forcing and compressive forcing. It is shown that these two limiting cases yield significantly different turbulence statistics and star formation rates. Different observed regions also show evidence of different mixtures of compressive and solenoidal forcing. This work should be useful for both observational and theoretical astrophysicists, as well as for readers interested in more general properties of interstellar turbulence and star formation, and in how these are modeled in computer simulations.
Author: Wolfram Schmidt Publisher: Springer Science & Business Media ISBN: 3319014757 Category : Science Languages : en Pages : 98
Book Description
In this "SpringerBrief" the author considers the underlying problems and questions that are common to numerical models of turbulence in different astrophysical systems. Turbulence has emerged as an important research topic in several areas of astrophysics. Understanding and modeling turbulence is particularly important for the dynamics of the interstellar medium, but also for the intergalactic medium, as well as in stars. The advancement of methods for numerical simulations of astrophysical turbulence, however, is still challenging because of gravity, strong compressibility, magnetic fields, and other effects. The book begins with a review of general aspects of numerical simulations of turbulence. In the main part the author presents findings from his numerical studies on astrophysical turbulence and discusses the astrophysical implications. He also explains in detail the numerical schemes utilized. Readers will find that this book offers a compact yet comprehensive introduction.
Author: Julia Duval Publisher: ISBN: Category : Languages : en Pages : 536
Book Description
Abstract: The Galactic Ring Survey, a 13 CO survey of the first quadrant of the Milky Way, is used to probe the spiral structure of the Galaxy and to constrain the formation and turbulent structure of molecular clouds. A sample of 829 molecular clouds has been identified in the Galactic Ring Survey (GRS). Kinematic distances to 750 of these GRS clouds are derived. The Galactic surface mass density of molecular gas is subsequently computed from 13 CO and 12 CO emission detected in the GRS and the University of Massachusetts-Stony Brook surveys. The Galactic distribution of molecular clouds is strongly enhanced along the Scutum-Crux, Sagittarius, and Perseus arms. These molecular data are consistent with a four-arm model of the Galaxy, while the locations of the Scutum-Crux and Perseus arms are consistent with the distribution of the old stellar population inferred from infrared maps. Physical properties of molecular clouds such as size, mass, and density, are also derived in order to compare clouds located inside and outside spiral arms, and to constrain formation models. Molecular clouds located inside inferred spiral arms are found to be more massive, to have higher surface mass densities, and to be more strongly gravitationally bound than inter-arm clouds. This supports cloud formation models involving spiral structure and suggests that molecular clouds must have lifetimes of a few million years. The turbulent structure of molecular clouds is a fundamental component of star formation. The GRS is the first large scale, fully sampled 13 CO survey of the Galaxy allowing the observation of the sub-parsec-scale structure of molecular clouds. Principal Component Analysis applied to both GRS clouds and numerical simulations allows the derivation of turbulent energy spectra over scales ranging from 0.1 pc to 50 pc. The slope of the energy spectrum, E(k), versus the wavenumber, k, obtained for the GRS clouds is consistent with compressible, intermittent turbulence. The slopes and amplitudes of the energy spectra of the clouds are fairly constant over three decades of masses, which indicates that turbulence is driven on large scales by an external, Galactic pool of kinetic energy.
Author: Nickolay Y. Gnedin Publisher: Springer ISBN: 3662478900 Category : Science Languages : en Pages : 375
Book Description
This book contains the elaborated and updated versions of the 24 lectures given at the 43rd Saas-Fee Advanced Course. Written by four eminent scientists in the field, the book reviews the physical processes related to star formation, starting from cosmological down to galactic scales. It presents a detailed description of the interstellar medium and its link with the star formation. And it describes the main numerical computational techniques designed to solve the equations governing self-gravitating fluids used for modelling of galactic and extra-galactic systems. This book provides a unique framework which is needed to develop and improve the simulation techniques designed for understanding the formation and evolution of galaxies. Presented in an accessible manner it contains the present day state of knowledge of the field. It serves as an entry point and key reference to students and researchers in astronomy, cosmology, and physics.
Author: Mikhail Ya Marov Publisher: Springer Science & Business Media ISBN: 1461451558 Category : Science Languages : en Pages : 682
Book Description
The book deals with the development of continual models of turbulent natural media. Such models serve as a ground for the statement and numerical evaluation of the key problems of the structure and evolution of the numerous astrophysical and geophysical objects. The processes of ordering (self-organization) in an originally chaotic turbulent medium are addressed and treated in detail with the use of irreversible thermodynamics and stochastic dynamics approaches which underlie the respective models. Different examples of ordering set up in the natural environment and outer space are brought and thoroughly discussed, the main focus being given to the protoplanetary discs formation and evolution.
Author: Jonathan J. Carroll-Nellenback
Author: Jonathan J. Carroll-Nellenback
Author: José Franco
Author: Christoph Federrath
Author: Wolfram Schmidt
Author: Julia Duval
Author: Mikhail Ya Marov
Author: Douglas F.A. Boyd
Author: Nickolay Y. Gnedin
Author: Henrik Beuther
Author: Mikhail Ya Marov