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Author : Peter K. Sollins
Publisher :
ISBN 13 :
Total Pages : 163 pages
Book Rating : 4.:/5 (625 download)
Download or read book Accretion and Outflow in Massive Star Formation written by Peter K. Sollins and published by . This book was released on 2005 with total page 163 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Author : Lee Hartmann
Publisher : Cambridge University Press
ISBN 13 : 9780521785204
Total Pages : 260 pages
Book Rating : 4.7/5 (852 download)
Download or read book Accretion Processes in Star Formation written by Lee Hartmann and published by Cambridge University Press. This book was released on 2000-11-15 with total page 260 pages. Available in PDF, EPUB and Kindle. Book excerpt: This first comprehensive account of the dynamical processes in the formation of stars and disks from which planets ultimately form.
Author : Peter Bodenheimer
Publisher : Springer Science & Business Media
ISBN 13 : 3642150632
Total Pages : 352 pages
Book Rating : 4.6/5 (421 download)
Download or read book Principles of Star Formation written by Peter Bodenheimer and published by Springer Science & Business Media. This book was released on 2011-07-10 with total page 352 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding star formation is one of the key fields in present-day astrophysics. This book treats a wide variety of the physical processes involved, as well as the main observational discoveries, with key points being discussed in detail. The current star formation in our galaxy is emphasized, because the most detailed observations are available for this case. The book presents a comparison of the various scenarios for star formation, discusses the basic physics underlying each one, and follows in detail the history of a star from its initial state in the interstellar gas to its becoming a condensed object in equilibrium. Both theoretical and observational evidence to support the validity of the general evolutionary path are presented, and methods for comparing the two are emphasized. The author is a recognized expert in calculations of the evolution of protostars, the structure and evolution of disks, and stellar evolution in general. This book will be of value to graduate students in astronomy and astrophysics as well as to active researchers in the field.
Author : Henrik Beuther
Publisher :
ISBN 13 :
Total Pages : 514 pages
Book Rating : 4.F/5 ( download)
Download or read book Massive Star Formation written by Henrik Beuther and published by . This book was released on 2008 with total page 514 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Outflow Feedback Regulated Massive Star Formation in Parsec-Scale Cluster Forming Clumps written by and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: We investigate massive star formation in turbulent, magnetized, parsec-scale clumps of molecular clouds including protostellar outflow feedback using three dimensional numerical simulations of effective resolution 20483. The calculations are carried out using a block structured adaptive mesh refinement code that solves the ideal MHD equations including self-gravity and implements accreting sink particles. We find that, in the absence of regulation by magnetic fields and outflow feedback, massive stars form readily in a turbulent, moderately condensed clump of ≈ 1,600 M{sub {circle_dot}} (containing ≈ 102 initial Jeans masses), along with a cluster of hundreds of lower mass stars. The massive stars are fed at high rates by (1) transient dense filaments produced by large-scale turbulent compression at early times, and (2) by the clump-wide global collapse resulting from turbulence decay at late times. In both cases, the bulk of the massive star's mass is supplied from outside a 0.1 pc-sized 'core' that surrounds the star. In our simulation, the massive star is clump-fed rather than core-fed. The need for large-scale feeding makes the massive star formation prone to regulation by outflow feedback, which directly opposes the feeding processes. The outflows reduce the mass accretion rates onto the massive stars by breaking up the dense filaments that feed the massive star formation at early times, and by collectively slowing down the global collapse that fuel the massive star formation at late times. The latter is aided by a moderate magnetic field of strength in the observed range (corresponding to a dimensionless clump mass-to-flux ratio [lambda] ≈ a few); the field allows the outflow momenta to be deposited more efficiently inside the clump. We conclude that the massive star formation in our simulated turbulent, magnetized, parsec-scale clump is outflow-regulated and clump-fed (ORCF for short). An important implication is that the formation of low-mass stars in a dense clump can affect the formation of massive stars in the same clump, through their outflow feedback on the clump dynamics. In a companion paper, we discuss the properties of the lower mass cluster members formed along with the massive stars, including their mass distribution and spatial clustering.
Author : Roberto J. Galván-Madrid
Publisher : Springer Science & Business Media
ISBN 13 : 1461433088
Total Pages : 131 pages
Book Rating : 4.4/5 (614 download)
Download or read book On the Formation of the Most Massive Stars in the Galaxy written by Roberto J. Galván-Madrid and published by Springer Science & Business Media. This book was released on 2012-06-08 with total page 131 pages. Available in PDF, EPUB and Kindle. Book excerpt: The most massive stars in the galaxy - those with more than 15 to 20 solar masses - are lilkely to ionize their surroundings before they reach their final mass. How can they accrete in spite of the presence of over-pressurized gas? This thesis presents results of Submillimeter Array (SMA) and Very Large Array (VLA) studies of massive star formation regions in the early stages of ionization, as well as an analysis of numerical simulations of the evolution of these young HII regions. The results favor a picture in which very massive stars form in accretion flows that are partially ionized and that keep accreting material from their environment.
Author : Dimitri Mihalas
Publisher : Courier Corporation
ISBN 13 : 0486135888
Total Pages : 753 pages
Book Rating : 4.4/5 (861 download)
Download or read book Foundations of Radiation Hydrodynamics written by Dimitri Mihalas and published by Courier Corporation. This book was released on 2013-04-10 with total page 753 pages. Available in PDF, EPUB and Kindle. Book excerpt: Excellent, informative volume focuses on dynamics of nonradiating fluids, problems involving waves, shocks and stellar winds, physics of radiation, radiation transport, and the dynamics of radiating fluids. 1984 edition.
Author : Michael Mark Dunham
Publisher :
ISBN 13 :
Total Pages : 874 pages
Book Rating : 4.:/5 (676 download)
Download or read book Mass Accretion in the Embedded Phase of Low-mass Star Formation written by Michael Mark Dunham and published by . This book was released on 2010 with total page 874 pages. Available in PDF, EPUB and Kindle. Book excerpt: A long-standing problem in low-mass star formation is the "luminosity problem," whereby protostars are underluminous compared to the accretion luminosity expected both from theoretical collapse calculations and arguments based on the minimum accretion rate necessary to form a star within the embedded phase duration. In this dissertation, I present new research on protostars and the protostellar accretion process that addresses the luminosity problem in the following ways: I report new infrared detections of a very low luminosity protostar in Taurus and use all existing data ranging from the infrared through millimeter wavelengths to constrain radiative transfer models and determine physical properties of the source. I argue that the derived source luminosity is lower than that expected based on the properties of a previously detected molecular outflow driven by this source and suggest that this discrepancy can be resolved by variable rather than constant mass accretion. I report the discovery of a new protostar that is also driving a molecular outflow. Following a similar modeling procedure as above, I show that this source has an even lower luminosity that is once again inconsistent with that expected based on the properties of its outflow, again suggesting variable mass accretion. I present the results of a complete search for all protostars with luminosities less than or equal to that of our Sun in a new infrared survey of nearby star-forming regions. I identify 50 protostars with such luminosities. Only a small fraction (15-25%) of dense cores thought to be starless (not yet collapsing to form stars) in fact harbor low luminosity protostars. The distribution of luminosities of these 50 protostars is inconsistent with a constant protostellar mass accretion rate. I present a set of evolutionary models that start with existing models following the inside-out collapse of singular isothermal spheres and add isotropic scattering off dust grains, a circumstellar disk, two-dimensional envelope structure, mass-loss and the opening of outflow cavities, and a simple treatment of episodic mass accretion. I conclude that episodic mass accretion is both necessary and sufficient to resolve the luminosity problem.
Author : Ralph E. Pudritz
Publisher : Springer Science & Business Media
ISBN 13 : 9400929730
Total Pages : 652 pages
Book Rating : 4.4/5 (9 download)
Download or read book Galactic and Extragalactic Star Formation written by Ralph E. Pudritz and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 652 pages. Available in PDF, EPUB and Kindle. Book excerpt: Recent advances in the instrumentation used to observe star forming regions in both our own Milky Way and in external galaxies have transformed the subject from a phenomenological pursuit into an increasingly unified, physical science. High resolution centimetre, millimetre, infrared, and optical studies of local star forming clouds have allowed us to probe the physics of star formation down to spatial scales approaching those of the solar system. These developments make it possible to better constrain the basic physical processes underlying star formation itself. At the same time, these new instruments have placed extragalactic studies on a footing detailed enough to allow comparison with star forming regions within our own galaxy. This revolution means that we will soon be able to link the physics of local star forming regions to the global star forming properties of galaxies. The entire structure of this NATO Advanced Study Institute was designed to explore this new view of the subject. This Institute on "Galactic and Extragalactic Star Formation" was held from June 21 -July 4, 1987 at the Conference Centre in the village of Whistler, British Columbia, Canada. The informal atmosphere of this lovely mountain resort stim ulated many valuable scientific exchanges. The Institute was funded by a major grant from NATO Scientific Affairs. Additional financial and I.I1oral assistance was provided by the Canadian Institute for Theoretical Astrophysics (CITA) and Mc Master University.
Author : Derek Ward-Thompson
Publisher : Cambridge University Press
ISBN 13 : 1139494473
Total Pages : 229 pages
Book Rating : 4.1/5 (394 download)
Download or read book An Introduction to Star Formation written by Derek Ward-Thompson and published by Cambridge University Press. This book was released on 2011-02-10 with total page 229 pages. Available in PDF, EPUB and Kindle. Book excerpt: Guiding the reader through all the stages that lead to the formation of a star such as our Sun, this advanced textbook provides students with a complete overview of star formation. It examines the underlying physical processes that govern the evolution from a molecular cloud core to a main-sequence star, and focuses on the formation of solar-mass stars. Each chapter combines theory and observation, helping readers to connect with and understand the theory behind star formation. Beginning with an explanation of the interstellar medium and molecular clouds as sites of star formation, subsequent chapters address the building of typical stars and the formation of high-mass stars, concluding with a discussion of the by-products and consequences of star formation. This is a unique, self-contained text with sufficient background information for self-study, and is ideal for students and professional researchers alike.
Author : F. Palla
Publisher : Springer Science & Business Media
ISBN 13 : 3540316337
Total Pages : 242 pages
Book Rating : 4.5/5 (43 download)
Download or read book Physics of Star Formation in Galaxies written by F. Palla and published by Springer Science & Business Media. This book was released on 2006-07-06 with total page 242 pages. Available in PDF, EPUB and Kindle. Book excerpt: The book begins with a historical introduction, "Star Formation: The Early History", that presents new material of interest for students and historians of science. This is followed by two long articles on "Pre-Main-Sequence Evolution of Stars and Young Clusters" and "Observations of Young Stellar Objects". These articles on the fascinating problem of star formation from interstellar matter give a thorough overview of present-day theories and observations. The articles contain material so far unpublished in the astronomical literature. The book addresses graduate students and can be used as a textbook for advanced courses in stellar astrophysics.
Author : Jacques Lépine
Publisher : Springer Science & Business Media
ISBN 13 : 1402026005
Total Pages : 406 pages
Book Rating : 4.4/5 (2 download)
Download or read book Open Issues in Local Star Formation written by Jacques Lépine and published by Springer Science & Business Media. This book was released on 2006-04-18 with total page 406 pages. Available in PDF, EPUB and Kindle. Book excerpt: The international colloquium Open Issues in Local Star Formation and Early Stellar Evolution was focused on: the physics of young stellar objects, which are observed with increasing angular resolution by the new generation of telescopes; and the processes that triggered large scale star formation in the solar neighbourhood. The scientific presentations were not limited to these two main topics as many new and interesting results related to star formation have been obtained.; The participants presented new findings in the fields of stellar groups and associations; young stellar objects; disks; outflows and jets; the ISM conditions for star formation; and early stages of star formation. The discussions on open issues, representing problems and unanswered questions, should make this book particularly useful for researchers and PhD students.
Author : Mark R Krumholz
Publisher : World Scientific Publishing Company
ISBN 13 : 9813142057
Total Pages : 528 pages
Book Rating : 4.8/5 (131 download)
Download or read book Star Formation written by Mark R Krumholz and published by World Scientific Publishing Company. This book was released on 2017-05-11 with total page 528 pages. Available in PDF, EPUB and Kindle. Book excerpt: 'Krumholz has a strong writing style, didactic to be sure, but also fairly conversational within the limits of the material. While hardly casual reading, this text would be a good resource for a stellar astrophysicist, or any individual seeking to become one.'CHOICEThis book provides a modern introduction to the study of star formation, at a level suitable for graduate students or advanced undergraduates in astrophysics. The first third of the book provides a review of the observational phenomenology and then the basic physical processes that are important for star formation. The remainder then discusses the major observational results and theoretical models for star formation on scales from galactic down to planetary. The book includes recommendations for complementary reading from the research literature, as well as five problem sets with solutions.
Author : Charles J. Lada
Publisher : Springer Science & Business Media
ISBN 13 : 9401136424
Total Pages : 779 pages
Book Rating : 4.4/5 (11 download)
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.
Author : Amadeu J. L. Fernandes
Publisher : Springer Science & Business Media
ISBN 13 : 9781402016172
Total Pages : 288 pages
Book Rating : 4.0/5 (161 download)
Download or read book Jets in Young Stellar Objects written by Amadeu J. L. Fernandes and published by Springer Science & Business Media. This book was released on 2004 with total page 288 pages. Available in PDF, EPUB and Kindle. Book excerpt: The ubiquity of jet phenomena in young stellar objects, active galactic nuclei, symbiotic stars, planetary nebulae and x-ray binaries has driven a broad literature on the astrophysics of collimated mass ejection. One of the fundamental open problems in star formation is the understanding of the physical mechanisms by which mass is ejected from the protostellar system and collimated into jets. Locally, jets will regulate the system's angular momentum and therefore its evolution during the first few million years. At large scale, jets inject momentum into the cloud thus affecting its star formation efficiency and evolution.Many recent advances over the last years in the star-formation research (both theory and observations) together with the increasing availability of computational resources, provided an excellent opportunity to organise a workshop. This volume presents the results of the workshop discussions on the jet phenomenon on different astrophysical scales and covers interdisciplinary areassuch as steady state winds, time-dependent winds/jets, jet energetics and jet/wind propagation.
Author : Raphaël Mignon-Risse
Publisher :
ISBN 13 :
Total Pages : 0 pages
Book Rating : 4.:/5 (125 download)
Download or read book On the Formation of Massive Stars written by Raphaël Mignon-Risse and published by . This book was released on 2020 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Understanding the formation of low- and high-mass stars is a fundamental challenge of modern astronomy. They form from the collapse of gravitationally-unstable cores, in the interstellar medium which is nothing but simple to model: energies of gravity, turbulence, magnetic fields, radiation, and cosmic-rays are close to equipartition. Hence, numerical simulations are of a great help in studying star formation. In this work, we have focused on the formation of massive stars, which are very luminous and power a strong radiative force which can, in a simple unidimensional view, stop further accretion of material. Multi-dimensional simulations and particular treatment of stellar radiation are two main ingredients. In that view, the main task of the present thesis has been the numerical coupling between two radiative transfer methods. With this new tool, we have focused on three axes: the mechanisms of accretion, of ejection, and the formation of multiple stellar systems.The very heart of this thesis has been the numerical coupling between two radiative transfer methods into the RAMSES code (Teyssier, 2002), and its validation through pure radiative transfer benchmark tests. Then, we have applied this method in a radiation-hydrodynamical context of a massive pre-stellar core collapse. We have shown that the radiative force is enhanced, in comparison to the previous method used, ending up in the formation of larger radiative cavities and slightly less accretion. More importantly, we have tested the presence and accretion via radiative Rayleigh-Taylor instabilities at the border of these cavities, whose existence was an active debate in the community. We have shown their absence in our simulations to be of physical, rather than numerical, origin.In an on-going side-project carried in collaboration with A. Oliva and R. Kuiper (Univ. of Tübingen), we have led a comparison study between our respective codes, when it comes to modelling accretion disk fragmentation and subsequent formation of multiple stellar systems. With a Cartesian grid (instead of their spherical grid), our results show the formation of a binary or triple system, while they obtained a single star. When a multiple system is sufficiently dominated in mass by a single object, our codes show correct agreement on the disk rotation profile and temperature structure.Finally, we have run original simulations of turbulent magnetized cores with ambipolar diffusion and the newly implemented hybrid radiative transfer method. We have identified the magnetic tower flow as the dominant outflow mechanism, except very close to the massive protostar where radiative force dominates. We have compared these outflow properties to those obtained from observational statistical samples. Our results tend to show a good agreement, provided our initial conditions are representative of the least massive progenitors of high-mass stars, and the collimation is not intrinsic to the outflow mechanism but also depends on environmental factors. Hence, these questions need to be further investigated. We have identified disk-mediated accretion as the only accretion mechanism, with disk sizes significantly smaller than predicted by the radiation-hydrodynamical simulations, and in agreement with recent low-mass star formation results. Eventually, we have questioned the disk-outflow-magnetic fields alignment. Our results are consistent with a random disk-magnetic field alignment and a slightly better outflow-magnetic field alignment, provided the medium is not too turbulent.
Author : Steven W. Stahler
Publisher : John Wiley & Sons
ISBN 13 : 3527618686
Total Pages : 865 pages
Book Rating : 4.5/5 (276 download)
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.
