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 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 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 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 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 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 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 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 Morphology Fragmentation and Dynamic Balance an Investigation Into Early Stages of Structure Formation in Molecular Clouds written by Shashwata Ganguly and published by . This book was released on 2022 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Present day and Early Star Formation written by Anne-Katharina Jappsen and published by Sudwestdeutscher Verlag Fur Hochschulschriften AG. This book was released on 2009 with total page 152 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stars form from molecular cloud cores by gravoturbulent fragmentation. Understanding the angular momentum and the thermal evolution of cloud cores thus plays a fundamental role in completing the theoretical picture of star formation. This is true not only for current star formation as observed in regions like the Orion nebula or the -Ophiuchi molecular cloud but also for the formation of stars of the first or second generation in the universe. In this thesis we show how the angular momentum of prestellar and protostellar cores evolves and compare our results from hydrodynamical simulations with observed quantities. We find that collapse induced by gravoturbulent fragmentation is accompanied by a substantial loss of specific angular momentum. This eases the "angular momentum problem" in star formation. The distribution of stellar masses at birth (the initial mass function, IMF) is another aspect that any theory of star formation must explain. Our investigation generally supports the idea that the distribution of stellar masses depends mainly on the thermodynamic state of the gas.
Download or read book The Earliest Stages of Massive Clustered Star Formation Fragmentation of Infrared Dark Clouds written by Ke Wang and published by Springer. This book was released on 2014-11-03 with total page 160 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis presents an in-depth, high-resolution observational study on the very beginning of the formation process: the fragmentation of dense molecular clouds known as infrared dark clouds (IRDCs). Using the Submillimeter Array (SMA) and Very Large Array (VLA) radio interferometers, the author has discovered a common picture of hierarchical fragmentation that challenges some of the leading theoretical models and suggests a new, observation-driven understanding of how massive star formation in clustered environments may begin: it is initiated by the hierarchical fragmentation of a dense filament from 10 pc down to 0.01 pc, and the stellar mass buildup is simultaneously fed by hierarchical accretion at similar scales. The new scenario points out the importance of turbulence and filamentary structure, which are now receiving increasing attention and further tests from both observers and theorists.
Download or read book Astronomical Data Analysis Software and Systems XVI written by Richard A. Shaw and published by . This book was released on 2007 with total page 792 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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...
Download or read book The Physics of Star Formation and Early Stellar Evolution written by Charles J. Lada and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 779 pages. Available in PDF, EPUB and Kindle. Book excerpt: The origin of stars is one of the principle mysteries of nature. During the last two decades advances in technology have enabled more progress to be made in the quest to understand stellar origins than at any other time in history. The study of star formation has developed into one of the most important branches of mod ern astrophysical research. A large body of observational data and a considerable literat ure now exist concerning this topic and a 1arge community of international astronomers and physicists devote their efforts attempting to decipher the secrets of stellar birth. Yet, the young astronomerjphysicist or more advanced researcher desiring to obtain a basic background in this area of research must sift through a very diverse and sometimes bewildering literature. A literature which includes research in many discip1ines and sub discip1ines of classical astrophysics from stel lar structure to the interstellar medium and encompasses the entire range of the electromagnetic spectrum from radio to gamma rays. Often, the reward of a suc cessfu1 foray through the current literature is the realization that the results can be obsolete and outdated as soon as the ink is dry in the journal or the conference proceeding in which they are published.
Download or read book The Birth of Star Clusters written by Steven Stahler and published by Springer. This book was released on 2017-11-04 with total page 205 pages. Available in PDF, EPUB and Kindle. Book excerpt: All stars are born in groups. The origin of these groups has long been a key question in astronomy, one that interests researchers in star formation, the interstellar medium, and cosmology. This volume summarizes current progress in the field, and includes contributions from both theorists and observers. Star clusters appear with a wide range of properties, and are born in a variety of physical conditions. Yet the key question remains: How do diffuse clouds of gas condense into the collections of luminous objects we call stars? This book will benefit graduate students, newcomers to the field, and also experienced scientists seeking a convenient reference.
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.
