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Author: International Astronomical Union. Symposium Publisher: Cambridge University Press ISBN: 9780521863469 Category : Science Languages : en Pages : 509
Book Description
New stars form in the dense turbulent gas clouds of galaxies, and the formation of these clouds is the subject of the IAU S237. This book is the most up-to-date review of all aspects of cloud and star formation, and one of the few compendiums available on ISM turbulence.
Book Description
This course-tested textbook conveys the fundamentals of magnetic fields and relativistic plasma in diffuse cosmic media, with a primary focus on phenomena that have been observed at different wavelengths. Theoretical concepts are addressed wherever necessary, with derivations presented in sufficient detail to be generally accessible. In the first few chapters the authors present an introduction to various astrophysical phenomena related to cosmic magnetism, with scales ranging from molecular clouds in star-forming regions and supernova remnants in the Milky Way, to clusters of galaxies. Later chapters address the role of magnetic fields in the evolution of the interstellar medium, galaxies and galaxy clusters. The book is intended for advanced undergraduate and postgraduate students in astronomy and physics and will serve as an entry point for those starting their first research projects in the field.
Book Description
Interstellar molecular clouds are generally believed to be the sites of active star formation in our galaxy. Observed densities, temperatures, and magnetic field strengths imply that well-ordered magnetic fields dominate thermal pressure in supporting these objects against self-gravity. The magnetic force is transferred to the neutrals through collisions with ions. Because the degree of ionization drops as the density increases, redistribution of the mass-to-flux ratio in a cloud's central flux tubes (ambipolar diffusion) takes place at an ever-increasing rate, leading to the formation of high-density cores, typically after 8 million years of quasi-static contraction. Eventually, the central mass-to-flux ratio exceeds the critical value for collapse, and the core begins to contract rapidly. We solve numerically the full non-linear, non-ideal MHD equations by using a new, non-orthogonal, fully adaptive grid describing the evolution of a set of non-rotating, axially symmetric model clouds. We follow the evolution from a central density $nsb{rm c}$ of 300 cm$sp{-3}$ to 10$sp9$ cm$sp{-3}$, at which point the calculation is stopped because the relation for the ionization fraction and the assumption of isothermality begin to break down. The central field strength $Bsb{rm c}$ increases from 16-120 microgauss to 1-5 milligauss for the ranges of initial values of the dimensionless parameters studied. Even when the final degree of ionization is a factor of 80 smaller than in the typical case, the field lines are pulled inward in the core during its rapid collapse. In the relation $Bsb{rm c} propto nsb{rm c}spkappa$, we find 0.42 $leq kappa leq$ 0.48. The central mass-to-flux ratio increases by a factor of from 10 (for canonical parameter values) up to 60 (for initial states that are a factor of 10 magnetically subcritical, and also for models that have relatively few ions, where most of the increase occurs during dynamical collapse). The extended envelope retains its magnetic support long after the core contracts.
Book Description
This volume contains the proceedings from the conference "The Labyrinth of Star Formation" that was held in Crete, Greece, in June 2012, to honour the contributions to the study of star formation made by Professor Anthony Whitworth of Cardiff University. The book covers many aspects of theoretical and observational star formation: low-mass star formation; young circumstellar discs; computational methods; triggered star formation; the stellar initial mass function; high-mass star formation and stellar clusters. Each section starts with a review paper, followed by papers discussing recent theoretical and observational work. This volume summarises our current understanding of star formation and is useful for both graduate students and researchers alike.
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Author: James Glynn Hosking
Author: Susan Elizabeth Byleveld
Author: International Astronomical Union. Symposium
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