Download or read book Fragmentation of Molecular Clouds and Star Formation written by E. Falgarone and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 557 pages. Available in PDF, EPUB and Kindle. Book excerpt: A few years ago, a motivation for organizing one more IAU Symposium on star for mation in Grenoble, was the anticipated completion of the IRAM interferometer on the Plateau de Bures, close to Grenoble. This choice was also a sort of late celebration of the genius of Joseph Fourier, born in Grenoble, whose work is the very fondation of in terferometry. At the time when we finally announced the advent of this conference, the first reactions we got from the community were expressions of saturation and even reject, the Symposium being unfortunately scheduled almost simultaneously as two other major meetings on closely related topics, and sponsored by different organizations. A wave of disappointment then reached the organizers. Some of us were enthusiastic enough to help the others overcome their discouragement. Let them be thanked here. There was, indeed, a deeper motivation for organizing this conference. It was to trigger the meeting and communication of physicists and astrophysicists since many of the difficulties met now in understanding the physics of the interstellar medium and its evolution toward star formation are common to several, if not most, other fields of physics. They are assigned to one origin: complexity.
Download or read book Observational Studies of Fragmentation in Molecular Clouds written by Riwaj Pokhrel and published by . This book was released on 2019 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: In this dissertation, I explore fragmentation physics in multiple scales in nearby molecular clouds and discuss some implications of fragmentation for cloud structure formation and star formation, primarily by analyzing multi-wavelength observations of dust emission. First, I tested the complete thermal and combined thermal and nonthermal support mechanisms that balance gravitational contraction at multiple scales in the Perseus molecular cloud. I found that the observed multiscale structures in Perseus are consistent with an inefficient thermal Jeans fragmentation, where the Jeans efficiency increases from the largest scale ($\gtrsim$10s of pc) to the smallest scale ($\sim$10s of AU). Next, I studied the effect of the formation of dense self-gravitating structures and star formation on the gas distribution in terms of its column density distribution function (N-PDF). I found that the evolutionary effect of clouds has corresponding changes on the N-PDF functional form, with a lognormal shape in diffuse regions that have negligible star formation, a lognormal and two power-laws in denser regions with moderate star formation, and a lognormal and one power-law in the densest regions with highly efficient clustered star formation. Finally, I explored the variations of star and gas surface densities in twelve molecular clouds using various techniques. I found that the stellar mass surface density of the recently formed stars varies as the square of the gas mass surface density in all twelve clouds. Also, I do not find any evidence of a column density threshold for efficient star formation.
Download or read book Fragmentation of molecular clouds written by Ralf S. Klessen and published by . This book was released on 1998 with total page 183 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fragmentation of Molecular Clouds and Star Formation written by E. Falgarone and published by Springer. This book was released on 1991-03-31 with total page 556 pages. Available in PDF, EPUB and Kindle. Book excerpt: A few years ago, a motivation for organizing one more IAU Symposium on star for mation in Grenoble, was the anticipated completion of the IRAM interferometer on the Plateau de Bures, close to Grenoble. This choice was also a sort of late celebration of the genius of Joseph Fourier, born in Grenoble, whose work is the very fondation of in terferometry. At the time when we finally announced the advent of this conference, the first reactions we got from the community were expressions of saturation and even reject, the Symposium being unfortunately scheduled almost simultaneously as two other major meetings on closely related topics, and sponsored by different organizations. A wave of disappointment then reached the organizers. Some of us were enthusiastic enough to help the others overcome their discouragement. Let them be thanked here. There was, indeed, a deeper motivation for organizing this conference. It was to trigger the meeting and communication of physicists and astrophysicists since many of the difficulties met now in understanding the physics of the interstellar medium and its evolution toward star formation are common to several, if not most, other fields of physics. They are assigned to one origin: complexity.
Download or read book The Earliest Fragmentation in Molecular Clouds written by Rowan Johnston Smith and published by . This book was released on 2010 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Formation of Stars written by Steven W. Stahler and published by John Wiley & Sons. This book was released on 2008-07-11 with total page 865 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is a comprehensive treatment of star formation, one of the most active fields of modern astronomy. The reader is guided through the subject in a logically compelling manner. Starting from a general description of stars and interstellar clouds, the authors delineate the earliest phases of stellar evolution. They discuss formation activity not only in the Milky Way, but also in other galaxies, both now and in the remote past. Theory and observation are thoroughly integrated, with the aid of numerous figures and images. In summary, this volume is an invaluable resource, both as a text for physics and astronomy graduate students, and as a reference for professional scientists.
Download or read book Turbulence and Fragmentation in Molecular Clouds written by Fabian Heitsch and published by . This book was released on 2001 with total page 75 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Earliest Stages of Massive Clustered Star Formation written by Ke Wang and published by . This book was released on 2014-11-30 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Recent Advances in the Collapse and Fragmentation of Turbulent Molecular Cloud Cores written by and published by . This book was released on 2002 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The formation of Giant Molecular Clouds (GMCs) sets the stage for the formation of protostellar systems by the gravitational collapse of dense regions within the GMC that fragment into smaller core components that in turn condense into stars. Developing a comprehensive theory of star formation remains one of the most elusive, and most important, goals of theoretical astrophysics. Inherent in the difficulty in attaining this goal is that the gravitational collapse depends critically upon initial conditions within the cores which only recently have been known with sufficient accuracy to permit a realistic theoretical attack on the problem. Observations of stars in the vicinity of the Sun show that binary systems are prevalent and appear to be a general outcome of the collapse and fragmentation process. Despite years of progress, theoretical studies have still not determined why binary stars occur with such frequency, or indeed, even what processes determine the transition from single stars to binaries and thence to multiple stellar systems. One of the major goals of this research is to understand the nature of the formation of binary and multiple stellar systems with typical low mass stars 0.2 to 3 M{sub {circle_dot}} and the physical properties of these systems. Basic questions concerning this process remain unanswered. What determines the fraction of an unstable cloud that will fragment into protostellar objects? What determines the pattern of stellar clustering into binaries and multiple systems? Even after fragmentation occurs, we have little understanding of the subsequent collapse. Consequently, it is unclear how the mass distribution of fragments maps onto eventual stellar masses, something we must understand to explain the stellar initial mass function (IMF). We will first discuss the development of the numerical methodology that will contribute to answering these questions. This technology consists of a 3D parallel, adaptive mesh refinement (AMR) self-gravitational, radiation-hydrodynamics code that we have developed. We will present new results for the gravitational collapse and fragmentation of marginally stable turbulent molecular cloud cores and follow the collapse of high mass fragments as they interact with the radiation of the protostars forming at their centers. We will discuss the theoretical difficulties in forming binary stars and the role of turbulence in their formation.
Download or read book Dynamics of molecular clouds turbulent fragmentation and star formation written by P. Padoan and published by . This book was released on 1997 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physical Processes in Fragmentation and Star Formation written by Roberto Capuzzo-Dolcetta and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent years have witnessed the expansion and multiplication of the observations of star formation and fragmentation accompanied by a consequent growth in the study of the underlying physical processes, the chemistry, the sites, the times, etc. Moreover, recent studies have shown that the formation of stars is likely to share many features with the formation of other self-gravitating objects. The present volume, therefore, discusses the formation of such objects in a systematic and comparative manner.
Download or read book Molecular Clouds in Galaxies with Different Z written by José Franco and published by . This book was released on 1986 with total page 12 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Fragmentation of Magnetically supported Weakly ionized Molecular Clouds written by Duncan A. Christie and published by . This book was released on 2011 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We follow the evolution and fragmentation of isolated, magnetically-supported, weakly- ionized, self-gravitating molecular clouds in three dimensions. Although the model clouds are supported by the magnetic field, high-density, magnetically-supercritical fragments form due to the drift between the ions and the neutrals, ambipolar diffusion. To follow the evolution of the model clouds, we extended the publicly-available Zeus-MP code to include the effects of nonideal magnetohydrodynamics and have modified several algo- rithms to improve accuracy and convergence. We present the results of a parameter study which varies the ionization fraction, mass-to-flux ratio, and velocity perturbation in the model clouds.
Download or read book Physical Processes in Interstellar Clouds written by G.E. Morfill and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 551 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book is the result of a meeting held in August, 1986 in Irsee, West Germany. As the title suggests, the aim of the meeting was to discuss physical processes in interstellar clouds, determine the current status, aims and future direction of the research in this area. Interstellar clouds contain nearly all the mass of diffuse gas in our galaxy, some 10% of the total galactic mass. They represent the birth site for stars and the final "dumping ground" for matter ejected from stars (winds, ex plosive ejecta) and thus play an integral part in the galactic recycling of material. Not only are the clouds important for the structure and evolution of our galaxy, they are also interesting objects of study "per se". Because of their vast scales (up to about 100 parsec), extreme temperatures (as low as about lOOK), and long life 8 times (estimated a about 10 years) a number of physical and chemical processes occur in these environments, which we are not able to study elesewhere, certainly not in laboratories. It is for this reason that the meeting, and hence this book, was organized in such a way that firstly the latest observational results were sum m~ized, going from the global, large scales, to finer details and dynamics, then progressing onwards to the processes -dynamical, chemical, electromagnetic, etc.
Download or read book Molecular Clouds written by R. A. James and published by Cambridge University Press. This book was released on 1991-06-28 with total page 362 pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of molecular clouds has received increasing interest over recent years, particularly in the UK with the advent of powerful new instruments such as MERLIN and the Maxwell millimetre wave telescope. This book is based on the proceedings of the Seventh Manchester International Astronomy Conference which brought together an international list of speakers to discuss important new developments in this field. The book covers a wide range of topics relevant to the general subject of molecular clouds, with review articles and papers from an impressive list of contributors. Much new work in this area is covered, and consequently this book should become an important reference source for workers in this and related fields.
Download or read book Molecular Clouds in the Milky Way and External Galaxies written by Robert L. Dickman and published by . This book was released on 1988 with total page 504 pages. Available in PDF, EPUB and Kindle. Book excerpt: The volume consists of up-to-date reviews and a selection of contributed papers on subjects including the structure and physical properties of molecular clouds, their role in the star formation process, their dust and chemical properties, molecular cloud surveys of the Milky Way, cloud evolution, problems in cloud mass determinations (a panel discussion and review), the CO properties of external galaxies, nuclei of galaxies as revealed by molecular observations, and galactic spiral structure as reflected by molecular cloud distributions. The abstracts of poster papers on these topics presented at the conference are also included. This book is both a valuable reference and a compendium of current knowledge in this field. It should be of special interest to all students and researchers who work on the physics of star formation, the interstellar medium, molecular clouds and galactic structure.
Download or read book Evolution of Interstellar Dust Grains in Molecular Cloud Envelopes written by Leire Beitia Antero and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Star formation takes place inside cold, dense clouds of molecular material (molecularclouds) that experience a hierarchical fragmentation process. Inside these clouds the material organises itself in lamentary structures, with a density increasing at smaller scales where stars are eventually formed. The evolution ofthese clouds is aected by the injection of energy into the system. It is now widely accepted that magnetohydrodynamic turbulence contributes to sustain a molecular cloud against collapse and in consequence, directly inuences the star formation eciency. Magnetic elds, therefore, are a fundamental shaping agent of molecular clouds. The most external layers of these clouds, the so-called molecular cloud envelopes, are partially ionised due to their exposure to the ambient radiation field and hence are eectively coupled to the magnetic field. This coupling favours the propagation of hydromagnetic waves inside the clouds, increasing the turbulent state of the gas...
