Download or read book Current Advances in the Computational Simulation of the Formation of Low Mass Stars written by R. I. Klein and published by . This book was released on 2005 with total page 20 pages. Available in PDF, EPUB and Kindle. Book excerpt: Developing a theory of low-mass star formation ({approx} 0.1 to 3 M{sub {circle_dot}}) remains one of the most elusive and important goals of theoretical astrophysics. The star-formation process is the outcome of the complex dynamics of interstellar gas involving non-linear interactions of turbulence, gravity, magnetic field and radiation. The evolution of protostellar condensations, from the moment they are assembled by turbulent flows to the time they reach stellar densities, spans an enormous range of scales, resulting in a major computational challenge for simulations. Since the previous Protostars and Planets conference, dramatic advances in the development of new numerical algorithmic techniques have been successfully implemented on large scale parallel supercomputers. Among such techniques, Adaptive Mesh Refinement and Smooth Particle Hydrodynamics have provided frameworks to simulate the process of low-mass star formation with a very large dynamic range. It is now feasible to explore the turbulent fragmentation of molecular clouds and the gravitational collapse of cores into stars self-consistently within the same calculation. The increased sophistication of these powerful methods comes with substantial caveats associated with the use of the techniques and the interpretation of the numerical results. In this review, we examine what has been accomplished in the field and present a critique of both numerical methods and scientific results. We stress that computational simulations should obey the available observational constraints and demonstrate numerical convergence. Failing this, results of large scale simulations do not advance our understanding of low-mass star formation.
Download or read book Protostars and Planets V written by Bo Reipurth and published by University of Arizona Press. This book was released on 2007 with total page 994 pages. Available in PDF, EPUB and Kindle. Book excerpt: 'Protostars and Planets V' builds on the latest results from recent advances in ground and space-based astronomy and in numerical computing techniques to offer the most detailed and up-to-date picture of star and planet formation - including the formation and early evolution of our own solar system.
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.
Download or read book The Labyrinth of Star Formation written by Dimitris Stamatellos and published by Springer Science & Business Media. This book was released on 2014-04-03 with total page 490 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book Tracing the mass during low mass star formation written by Chadwick Hayward Young and published by . This book was released on 2002 with total page 172 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Formation and Evolution of Low Mass Stars written by A.K. Dupree and published by Springer. This book was released on 2011-10-02 with total page 462 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book represents the Proceedings of the NATO Advanced Study Insti tute on Formation and Evolution of Low Mass Stars held from 21 September to 2 October 1987 at Viana do Castelo, Portugal. Holding the meeting in Portugal recognized both the historical aspects and the bright future of astronomy in Portugal. In the early sixteenth century, the Portugese played an important role in the critical diffusion of classical and medieval knowledge which formed so large a part of scientific activity at that time. Navigation and course setting, brought to a high level by Portugese explorers, relied on mathematics and astronomy to produce precise tables of solar positions. In contemporary Portu gal, astronomy is the focus of renewed interest and support at the universities. It is thus particularly appropriate that the NATO Advanced Study Institute was held on the coast of the Atlantic Ocean in the friendly surroundings of the Costa Verde.
Download or read book New Worlds New Horizons in Astronomy and Astrophysics written by National Research Council and published by National Academies Press. This book was released on 2011-02-04 with total page 324 pages. Available in PDF, EPUB and Kindle. Book excerpt: Driven by discoveries, and enabled by leaps in technology and imagination, our understanding of the universe has changed dramatically during the course of the last few decades. The fields of astronomy and astrophysics are making new connections to physics, chemistry, biology, and computer science. Based on a broad and comprehensive survey of scientific opportunities, infrastructure, and organization in a national and international context, New Worlds, New Horizons in Astronomy and Astrophysics outlines a plan for ground- and space- based astronomy and astrophysics for the decade of the 2010's. Realizing these scientific opportunities is contingent upon maintaining and strengthening the foundations of the research enterprise including technological development, theory, computation and data handling, laboratory experiments, and human resources. New Worlds, New Horizons in Astronomy and Astrophysics proposes enhancing innovative but moderate-cost programs in space and on the ground that will enable the community to respond rapidly and flexibly to new scientific discoveries. The book recommends beginning construction on survey telescopes in space and on the ground to investigate the nature of dark energy, as well as the next generation of large ground-based giant optical telescopes and a new class of space-based gravitational observatory to observe the merging of distant black holes and precisely test theories of gravity. New Worlds, New Horizons in Astronomy and Astrophysics recommends a balanced and executable program that will support research surrounding the most profound questions about the cosmos. The discoveries ahead will facilitate the search for habitable planets, shed light on dark energy and dark matter, and aid our understanding of the history of the universe and how the earliest stars and galaxies formed. The book is a useful resource for agencies supporting the field of astronomy and astrophysics, the Congressional committees with jurisdiction over those agencies, the scientific community, and the public.
Download or read book Investigations of Low mass Star Formation written by Stella Susannah Reber Offner and published by . This book was released on 2009 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Physics of Galaxy Formation written by Claudia Del P. Lagos and published by Springer Science & Business Media. This book was released on 2013-10-15 with total page 252 pages. Available in PDF, EPUB and Kindle. Book excerpt: This thesis addresses two of the central processes which underpin the formation of galaxies: the formation of stars and the injection of energy into the interstellar medium from supernovae, called feedback. In her work Claudia Lagos has completely overhauled the treatment of these processes in simulations of galaxy formation. Her thesis makes two major breakthroughs, and represents the first major steps forward in these areas in more than a decade. Her work has enabled, for the first time, predictions to be made which can be compared against new observations which probe the neutral gas content of galaxies, opening up a completely novel way to constrain the models. The treatment of feedback from supernovae, and how this removes material from the interstellar medium, is also likely to have a lasting impact on the field. Claudia Lagos Ph.D. thesis was nominated by the Institute for Computational Cosmology at Durham University as an outstanding Ph.D. thesis 2012.
Download or read book Star Formation in Galaxy Evolution Connecting Numerical Models to Reality written by Nickolay Y. Gnedin and published by Springer. This book was released on 2015-09-09 with total page 375 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.
Download or read book The First Stars written by Volker Bromm and published by Springer. This book was released on 2016-09-07 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: The formation of the first stars (Pop III stars) and galaxies is one of the great outstanding challenges in modern astrophysics and cosmology. The first stars are likely key drivers for early cosmic evolution and will be at the center of attention over the next decade. The best available space and ground-based telescopes like the Hubble Space Telescope probe the Universe to high redshifts and provide us with tantalizing hints; but they cannot yet directly detect the first generation of stars and the formation of the first galaxies. This is left as key science for future telecopes like the James Webb Space Telescope. This book is based in part on classroom tested lectures related to Pop III stars, but also draws from the author's review articles of the main physical principles involved. The book will thus combine pedagogical introductory chapters with more advanced ones to survey the cutting-edge advances from the frontier of research. It covers the theory of first star formation, the relation between first stars and dark matter, their impact on cosmology, their observational signatures, the transition to normal star formation as well as the assembly of the first galaxies. It will prepare students for interpreting observational findings and their cosmological implications.
Download or read book Adaptive Mesh Refinement Theory and Applications written by Tomasz Plewa and published by Springer Science & Business Media. This book was released on 2005-12-20 with total page 550 pages. Available in PDF, EPUB and Kindle. Book excerpt: Advanced numerical simulations that use adaptive mesh refinement (AMR) methods have now become routine in engineering and science. Originally developed for computational fluid dynamics applications these methods have propagated to fields as diverse as astrophysics, climate modeling, combustion, biophysics and many others. The underlying physical models and equations used in these disciplines are rather different, yet algorithmic and implementation issues facing practitioners are often remarkably similar. Unfortunately, there has been little effort to review the advances and outstanding issues of adaptive mesh refinement methods across such a variety of fields. This book attempts to bridge this gap. The book presents a collection of papers by experts in the field of AMR who analyze past advances in the field and evaluate the current state of adaptive mesh refinement methods in scientific computing.
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.
Download or read book Computational Star Formation IAU S270 written by João Alves and published by Cambridge University Press. This book was released on 2011-05-19 with total page 574 pages. Available in PDF, EPUB and Kindle. Book excerpt: The rapid advance of computer capabilities over the last two decades has opened up a new field of numerical simulations in which detailed physical models can be made to represent the most complex processes. IAU Symposium 270 reviews a wide range of topics relevant to computer modeling in the fields of interstellar gas dynamics, star formation and galactic dynamics. It includes numerical techniques for modeling physical processes such as self-gravitating, radiative magnetohydrodynamics, as well as novel hardware options for acceleration and a view into the future of computation. Observations of interstellar gas and star formation are also reviewed. This book is ideal for graduate students and researchers in the field of numerical astrophysics.
Download or read book Star Formation Rates of Galaxies written by Andreas Zezas and published by Cambridge University Press. This book was released on 2021-04-29 with total page 318 pages. Available in PDF, EPUB and Kindle. Book excerpt: Star-formation is one of the key processes that shape the current state and evolution of galaxies. This volume provides a comprehensive presentation of the different methods used to measure the intensity of recent or on-going star-forming activity in galaxies, discussing their advantages and complications in detail. It includes a thorough overview of the theoretical underpinnings of star-formation rate indicators, including topics such as stellar evolution and stellar spectra, the stellar initial mass function, and the physical conditions in the interstellar medium. The authors bring together in one place detailed and comparative discussions of traditional and new star-formation rate indicators, star-formation rate measurements in different spatial scales, and comparisons of star-formation rate indicators probing different stellar populations, along with the corresponding theoretical background. This is a useful reference for students and researchers working in the field of extragalactic astrophysics and studying star-formation in local and higher-redshift galaxies.
Download or read book The Effect of High mass Stars on Low mass Star Formation written by Monica Pozzo and published by . This book was released on 2001 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Illuminating The Star Clusters And Dwarf Galaxies by Multi scale Baryonic Simulations written by Moupiya Maji and published by . This book was released on 2018 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Over the past decade, advances in computational architecture have made it possiblefor the first time to investigate some of the fundamental questions around the birthand the growth of the building blocks of the universe; star clusters and galaxies. Inthese stellar and star-forming systems, baryonic physics play an important role indetermining their formation and evolution. Therefore, in my research, I have exploredstar-forming systems using high resolution baryonic cosmological simulations andexplored the origin of star clusters, anisotropic spatial distribution of satellite galaxiesand the effect of reionization on the evolution of dwarf galaxies.Observations of globular clusters show that they have universal lognormal massfunctions with a characteristic peak at 2 10^5MSun , although the origin of this peakeddistribution is unclear. Here I have investigated the formation and evolution of starclusters (SCs) in interacting galaxies using high-resolution hydrodynamical simulationsperformed with two different codes. I have found that massive star clusters in therange of 10^5.5 10^7.5 MSun form preferentially in extremely high-pressure gas cloudsin highly-shocked regions produced by galaxy interactions. These findings provide thefirst simulation confirmation of the analytical theory of high pressure induced clusterformation. Furthermore, these massive star clusters have quasi-lognormal initial massfunctions with a peak around 106 M . The number of clusters declines with timedue to destructive processes, but the shape and the peak of the mass functions do notchange significantly during the course of galaxy collisions. These results suggest thatgas-rich galaxy mergers provide a favorable environment for the formation of globularclusters and that the lognormal mass functions and the unique peak may originatefrom the extreme high-pressure conditions of the birth clouds and may survive thedynamical evolution.Observations of classical Milky Way satellites suggest that they are aligned in aplane inclined to the Galactic stellar disk, a phenomenon which later became knownas the disk of satellites(DoS). However, N-body simulations of galaxies predict anisotropic distribution of subhalos around the host galaxy and this discrepancy hasbeen strongly criticized as a failure of CDM. In this thesis, I have explored this highlydebated topic by reanalyzing the observations and exploring the satellite distributions in high-resolution baryonic simulations. In particular, I have demonstrated that asmall sample size can artificially produce a highly anisotropic spatial distributionand a strong clustering of the angular momenta of the satellites and have shownthat the current Milky way DoS is transient. Furthermore, I have analyzed twocosmological simulations using the same initial conditions of a Milky-Way-sizedgalaxy, an N-body run with dark matter only, and a hydrodynamic one with bothbaryonic and dark matter, and found that the hydrodynamic simulation producesa more anisotropic distribution of satellites than the N-body one. These resultssuggest that an anisotropic distribution of satellites in galaxies can originate frombaryonic processes in the hierarchical structure formation model, but the claimedhighly flattened, coherently rotating DoS of the Milky Way may be biased by the small number selection effect. Finally, I have investigated the distribution and kinematicsof satellites around a large sample of few thousand host galaxies in the Illustrissimulation and found that the DoS become more isotropic with increasing numberof satellites and no clear coherent rotation is found in most ( 90%) of the satellitesystems. Furthermore, their overall evolution indicates that the DoS may be part oflarge scale filamentary structure. These findings can help resolve the contradictoryclaims of DoS in galaxies and show that baryonic processes may be the key to solvethe so-called small scale CDM problems.Additionally, I have also explored the effects of reionization on the star formationhistories of dwarfs galaxies, using a cosmological hydrodynamic simulation of MilkyWay and its satellite galaxies. I have found that most dwarfs are extremely old systemsand star formation is quenched earlier in lower mass galaxies. During reionization,most of the lower mass dwarfs are destroyed while the remaining massive dwarfsbecome severely baryon deficient. The dwarf galaxies play a very important role inshaping the path of cosmic history, especially in terms of reionization. Observingand studying the ultra-faint dwarfs hold the key to understanding the physics of earlyuniverse in great depth.
