Download or read book Young Massive Star Clusters as Probes for Stellar Evolution Cluster Dynamics and Long Term Survival written by Boyke Rochau and published by . This book was released on 2011 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Not So Simple Stellar Populations in Star Clusters written by Chengyuan Li and published by Springer. This book was released on 2017-09-19 with total page 137 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on understanding the stellar populations of massive star clusters and aims to investigate the origin, evolution and properties of binary systems, their collision products, as well as the general characteristics (e.g. ages, metal content) of stellar population(s) in star clusters. It introduces the basic background knowledge of various stellar populations in star clusters as well as their formation, interaction and evolution and offers high impact observational results on our understanding of the formation and evolution mode of star clusters. Based on these discoveries, this book proposes a series of future projects that can shed light on these topics. The research introduced in this book reveals key features of star clusters formation and by extension how all stars formed in our universe.
Download or read book The Formation and Evolution of Massive Young Star Clusters written by Henny J. G. L. M. Lamers and published by . This book was released on 2004 with total page 632 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Dynamical Evolution of Young Star Clusters written by Richard James Allison and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Stars form in large clouds of cold, dense molecular gas. In these clouds the majority of stars do not form in isolation, but instead form in clusters. The formation of stars and their hos~ clusters are intrinsically linked, and thus to fully understand how stars form we must also understand the formation and early evolution of stellar clusters. The formation of stars is thought to be governed by the turbulent conditions inside these molecular clouds, and due to this the initial conditions of star formation are likely to be spatially complex and dynamically cool. In this Thesis we use fractal spatial distributions (D = 1.6,2.0,2.6 and 3.0) to mimic the complex initial conditions of star formation to investigate how the dynamical evolution of star clusters is affected by variations in the amount of primordial structure. We also use varying initial virial ratios (Q = 0.3, 0.4 and 0.5) to investigate what affect the initial kinematics have on a clusters dynamical evolution. I present a new method, based on the minimum spanning tree, which is able to determine and quantify the presence of mass segregation. The method is applied to observations of the ONe, ,vhich we find to be complexly mass segregated, with different levels of mass segregation depending on stellar mass. We find, contrary to common belief, that mass segregation can occur through purely dynamical processes on a short timescale (rv the initial cluster crossing time). We also find that the amount of dynamical mass segregation that occurs is dependant on both the initial structure and virial ratio, where cooler and more structured initial conditions tend to lead to more dramatic dynamical evolution. Additionally, we find that the clumpy and cool initial conditions also lead to the dynamical formation of high-mass multiple systems, which in turn can lead to the ejection of high-mass stars and the destruction of the host cluster itself.
Download or read book Formation and Early Evolution of Stellar Clusters written by Joshua E. Wall and published by . This book was released on 2019 with total page 126 pages. Available in PDF, EPUB and Kindle. Book excerpt: We describe a novel numerical method for the studying the formation and evolution of stellar clusters, Torch. This method combines the magnetohydrodynamics code Flash with the Astrophysical Multipurpose Software Environment, AMUSE. Once embedded into AMUSE, we combine Flash with the stellar evolution code SeBa, the N-body dynamics code ph4 and the multiple star system evolution module multiples to create a unique method for tracing the detailed evolution of stellar clusters through time. We then add units for radiation, stellar winds and supernovae, as well as a new star by star formation prescription to Flash that allows for star formation and stellar feedback to create and destroy star clusters and the interstellar gas they form from. The result is the most detailed star cluster formation code to date. We then demonstrate the use of these methods for studying binary star formation and the effects of stellar feedback. We find that massive dynamical binaries created in our simulations are consistent with observations. Further, we observe that wide dynamical binaries tighten due to gas dynamical friction, losing cluster energy to the natal gas, after which they are disrupted by stellar encounters. This supports theoretical predictions that embedded clusters may contract due to the interactions of gas and stars. We also find that while stellar feedback is effective at expelling gas from natal clusters, the clusters themselves remain bound even as they expand due to the loss of the binding potential of the gas. Finally, stellar clusters formed in our simulations mass segregate before the expulsion of their natal gas clouds, as expected from observations of young clusters in the Milky Way.
Download or read book Evolution of Stars and Stellar Populations written by Maurizio Salaris and published by John Wiley & Sons. This book was released on 2005-12-13 with total page 386 pages. Available in PDF, EPUB and Kindle. Book excerpt: Evolution of Stars and Stellar Populations is a comprehensive presentation of the theory of stellar evolution and its application to the study of stellar populations in galaxies. Taking a unique approach to the subject, this self-contained text introduces first the theory of stellar evolution in a clear and accessible manner, with particular emphasis placed on explaining the evolution with time of observable stellar properties, such as luminosities and surface chemical abundances. This is followed by a detailed presentation and discussion of a broad range of related techniques, that are widely applied by researchers in the field to investigate the formation and evolution of galaxies. This book will be invaluable for undergraduates and graduate students in astronomy and astrophysics, and will also be of interest to researchers working in the field of Galactic, extragalactic astronomy and cosmology. comprehensive presentation of stellar evolution theory introduces the concept of stellar population and describes "stellar population synthesis" methods to study ages and star formation histories of star clusters and galaxies presents stellar evolution as a tool for investigating the evolution of galaxies and of the universe in general
Download or read book The Spatial Structure of Young Stellar Clusters written by Michael Kuhn and published by . This book was released on 2014 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Star formation is an extremely active area of astronomical research, and young stellar clusters in our Galaxy offer a useful laboratory where star-formation processes can be studied. Young stars form from the the gravitational collapse of molecular clouds that have a hierarchical spatial structure. This leads to stars forming in clustered environments, often with thousands of other young stars in environments that are strongly affected by feedback from massive O-type stars. The environments in these massive star-forming regions (MSFR) can affect how stars form and whether the young stellar clusters remain bound after star formation ends, both of which are questions that have received considerable attention from researchers. Studies of stellar populations in Galactic MSFRs are made difficult due to large numbers of fields stars in the Galactic Plane, large areas of the sky that must be surveyed, high optical extinction from dust, and nebulosity in the the optical and infrared. The Massive Young Star-Forming Complex Study in Infrared and X-ray (MYStIX) uses multiwavelength observations to overcome some of these difficulties, providing some of the most complete, clean membership lists for 20 MSFRs within 3.6 kpc of the Sun. I described X-ray catalogs and mid-infrared catalogs that were used in this survey. The spatial distribution of young stars in 17 MYStIX regions are used to probe the origin and dynamics of the young stellar clusters. Intrinsic stellar surface-density maps are made for each region, which reveal complex structures with dense subclusters. I examine in detail one of the nearest MYStIX young stellar clusters, W~40 (d=500 pc), which has properties similar to many of the subclusters in more massive and more distant star-forming regions. The cluster in W~40 has a simple structure with mass segregation, indicating that it has undergone dynamical evolution, even though its young age (~0.8 Myr) is insufficient for relaxation from two-body interactions. This apparent contradiction may be evidence of more rapid dynamical evolution accelerated by the merger of subclusters. Overall, 142 subclusters of young stars are found in the 17 MSFRs using the statistical "finite-mixture model" cluster analysis method, and the intrinsic stellar populations for these clusters are inferred using "initial mass functions" and "X-ray luminosity functions." Four structural classes are seen in MSFR: linear chains of subclusters, clumpy structures, core-halo structures, and simple isolated clusters. The subclusters do follow the structure of the molecular clouds, but do not appear to be coeval with each other. There is strong evidence in the subcluster properties for gas expulsion and subcluster expansion (e.g., the density~radius and age~radius relations), and evidence that is consistent with subcluster mergers (e.g., the ellipticity distribution and the number~density}$ relation). The cluster analysis provides evidence to support hierarchical models of stellar cluster formation, which have been theorized to explain mass segregation and dynamical relaxation in very young clusters. The ~1 Myr age spreads in the subclusters of a MSFR appear to require slower star-formation in giant molecular clouds with continually driven turbulence, rather than clouds with rapidly decaying turbulence. And, the diverse range of stellar surface density environment in MSFRs will have implications for models of cluster survival after gas removal.
Download or read book From Darkness to Light written by Thierry Montmerle and published by . This book was released on 2001 with total page 904 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annotation Approximately 90 papers from the April 2000 conference in Corsica, France discuss interstellar medium structure and magnetic fields, clouds and collapse, collapse and protostars, the origin of the initial mass function, cluster properties and evolution, pre-main sequence evolution, late evolution, and feedback mechanisms. Contributors include physicists, astronomers, and other scientists from Europe, Asia, and North and Soputh America. Sixteen pages of photographs from the conference are included. Annotation c. Book News, Inc., Portland, OR (booknews.com)
Download or read book Advances in Stellar Evolution written by Robert T. Rood and published by Cambridge University Press. This book was released on 1997-06-26 with total page 368 pages. Available in PDF, EPUB and Kindle. Book excerpt: An understanding of how stars evolve is central to astrophysics. The basic theory is well established. However, the subject has undergone a renaissance in recent years as powerful computers have become widely available and allowed complex evolutionary models to be developed and compared in great detail with observations from the latest instruments. This timely volume presents the review articles from an international meeting in Elba, Italy, where experts gathered to review how our understanding of stellar evolution has advanced. Topics covered include fundamentals of stellar evolution, star clusters, variable stars, asymptotic giant branch stars, degenerate stars, the evolution of binary stars, and chemical and galactic evolution. Throughout, theory and observation are closely compared. The book also emphasises the critical role stars have on our understanding of how galaxies evolve. In this book we are provided with both the fundamentals and the latest research. In this way, it will provide an invaluable supplement for graduate students, and a timely review for researchers.
Download or read book Old Open Clusters as Probes of Stellar and Galactic Disk Evolution written by Beth Robin Hufnagel and published by . This book was released on 1995 with total page 304 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Stars Stellar evolution written by Klaas de Boer and published by EDP Sciences. This book was released on 2012-12-17T00:00:00+01:00 with total page 333 pages. Available in PDF, EPUB and Kindle. Book excerpt: The diverse forms that stars assume in the course of their lives can all be derived from the initial conditions : the mass and the original chemical composition. In this textbook Stars and Stellar Evolution the basic concepts of stellar structure and the main roads of stellar evolution are described. First, the observable parameters are presented, which are based on the radiation emerging from a stellar atmosphere. Then the basic physics is described, such as the physics of gases, radiation transport, and nuclear processes, followed by essential aspects of modelling the structure of stars. After a chapter on star formation, the various steps in the evolution of stars are presented. This leads us to brown dwarfs, to the way a star changes into the red-giant state and numerous other stages of evolution and ultimately to the stellar ashes such as white dwarfs, supernovae and neutron stars. Stellar winds, stellar rotation and convection all influence the way a star evolves. The evolution of binary stars is included by using several canonical examples in which interactive processes lead to X-ray binaries and supernovae of type Ia. Finally, the consequences of the study of stellar evolution are tied to observed mass and luminosity functions and to the overall evolution of matter in the universe. The authors aim at reaching an understanding of stars and their evolution by both graduate students and astronomers who are not themselves investigating stars. To that end, numerous graphs and sketches, among which the Hertzsprung-Russell diagram is the dominant one, help trace the ways of stellar evolution. Ample references to specialised review articles as well as to relevant research papers are included.
Download or read book The Formation and Evolution of Star Clusters written by Kenneth Janes and published by . This book was released on 1991 with total page 613 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Star Clusters IAU S266 written by International Astronomical Union. Symposium and published by Cambridge University Press. This book was released on 2010-02-04 with total page 606 pages. Available in PDF, EPUB and Kindle. Book excerpt: Star clusters are important to many areas of astronomy, and as the basic building blocks of galaxies, they can be used as key diagnostic tools within a wide range of disciplines in astrophysics. Star cluster populations are powerful tracers of the formation, assembly and evolutionary history of their parent galaxies. Although their importance has been recognised for decades, only in recent years has this area seen a major investment in time and effort. IAU Symposium 266 consolidates the expertise of leading researchers from a variety of topical subfields in astrophysics, to provide a comprehensive presentation of cutting-edge developments in theory, observations and simulations of star clusters and star cluster systems across a range of sizes and epochs. This volume gives an account of this forefront research, answering fundamental questions that will improve our understanding of numerous related issues and show how this field will take its next major step forward.
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 Frontiers of Stellar Evolution written by David L. Lambert and published by . This book was released on 1991 with total page 656 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Time Domain Studies as a Probe of Stellar Evolution written by Adam Andrew Miller and published by . This book was released on 2013 with total page 283 pages. Available in PDF, EPUB and Kindle. Book excerpt: Stellar evolution proceeds on timescales of millions to billions of years, however, most stars in both the birthing and dying processes will punctuate their lives with short-lived (few days to a year) eruptions or explosions that lead to dramatic changes in the brightness of the star. Observational studies of these events are the foundation upon which time-domain astronomy is built. While these events are short lived, they often provide some of our most significant insights into stellar evolution. This dissertation focuses on the use of time-domain techniques to discover and characterize these rare astrophysical gems, while also addressing some gaps in our understanding of the earliest and latest stages of stellar evolution. The observational studies presented herein can be grouped into three parts: (i) the study of stellar death (supernovae); (ii) the study of stellar birth; and (iii) the use of modern machine-learning algorithms to discover and classify variable sources. I present observations of supernova (SN) 2006gy, the most luminous SN ever at the time of discovery, and the even-more luminous SN 2008es. Together, these two supernovae (SNe) demonstrate that core-collapse SNe can be significantly more luminous than thermonuclear type Ia SNe, and that there are multiple channels for producing these brilliant core-collapse explosions. For SN 2006gy I show that the progenitor star experienced violent, eruptive mass loss on multiple occasions during the centuries prior to explosion, a scenario that was completely unexpected within the cannon of massive-star evolution theory. I also present observations of SN 2008iy, one of the most unusual SNe ever discovered. Typical SNe take ≤3 weeks to reach peak luminosity; SN 2008iy exhibited a slow and steady rise for ~400 days before reaching maximum brightness. The best explanation for such behavior is that the progenitor of SN 2008iy experienced an episodic phase of mass loss ~100 yr prior to explosion. The three SNe detailed in this dissertation have altered our understanding of massive-star mass loss, namely, these SNe provide distinct evidence that post-main sequence mass loss, for at least some massive stars, occurs in sporatic fits, rather than being steady. They also demonstrate that core collapse is not restricted to the red supergiant and Wolf-Rayet stages of stellar evolution as theory predicted. Instead, some massive stars explode while in a luminous blue variable-like state. I also present observations of the newly discovered FU Orionis variable, PTF~10qpf. FU Orionis stars are young stellar objects (YSOs) that exhibit long-lasting (≥10 yr), large-amplitude (≥5 mag) eruptions due to accretion instabilities in the star+disk system. These eruptions, for which there are precious few examples, play an important role in (i) determining the final mass and angular momentum of the newly born star, (ii) clearing the circumstellar envelope from which the star forms, and (iii) the formation of planets, and ultimately life, in the circumstellar disk. PTF~10qpf is only the fourth FU Orionis variable with detailed observations taken during the course of eruption. Furthermore, it is the best observed FU Orionis star prior to eruption, with both optical spectra and infrared photometry demonstrating that the star was a normal classical T Tauri star before its outburst. This discovery shows that the FU Orionis phenomenon is not reserved for only the most-massive YSOs, as had previously been suggested. As robotic observing and automated data processing procedures render the standard transient discovery process mundane, we are quickly approaching an era where we will be overwhelmed with discoveries. The Large Synoptic Survey Telescope (LSST), with a planned start in 2020, is expected to discover ~50 million variable stars, an orders-of-magnitude leap over the currently known number of variables. As data volumes grow to these enormous sizes, it is clear that classical discovery and characterization techniques relying on the visual inspection of data are no longer tractable. In the final chapters of this dissertation, I present a scaleable machine-learning framework capable of identifying rare sources in a time-domain dataset, while also providing classifications for the most prevalent source types in the survey. Following a search of the variables identified in the All Sky Automated Survey, I discover four bright R Coronae Borealis stars, carbon-rich supergiants in a short-lived phase of late stellar evolution. The discovery of these stars, which were identified via a fully automated procedure, represent an important proof-of-concept demonstrating that advanced algorithmic procedures can unearth the rare astronomical sources that lead to leaps in our understanding of stellar evolution. I close with the presentation of a new machine-learning methodology for inferring the fundamental atmospheric properties of stars, Teff, log g, and [Fe/H], without obtaining spectra. While the development of these tools, which predict the atmospheric parameters from photometric light curves, are still in their infancy, I argue that their continued development will enable the conversion of large photometric time-domain surveys, such as LSST, into pseudo-spectrographs. Astrophysical science should no longer be viewed as a static tableau but instead as the unraveling of violent beginnings in a dynamic cosmos. The use of machine learning to extract novel results from large astronomical datasets occupies an instrumental portion of a burgeoning 21st century revolution in the way we conduct ourselves as scientists -- the poetic connection of this modern approach applied to the millennia-old practice of monitoring the heavens will uncover a universe of new mysteries.
Download or read book The Destructive Birth of Massive Stars Massive Star Clusters written by Anna L. Rosen and published by . This book was released on 2017 with total page 289 pages. Available in PDF, EPUB and Kindle. Book excerpt: The injection of energy and momentum into the interstellar medium by young massive stars' intense radiation fields and their fast, radiatively driven winds can have a profound influence on their formation and environment. Massive star forming regions are rare and highly obscured, making the early moments of their formation difficult to observe. Instead, we must turn to theory to elucidate the physics involved in the formation of massive stars and massive star clusters (MSCs), which can host thousands of massive stars. In my thesis, I developed analytical and numerical techniques to study the formation of massive stars and how stellar wind feedback affects the dynamics of gas that surrounds MSCs. To estimate the initial rotation rates of massive stars at birth, I developed a protostellar angular momentum evolution model for accreting protostars to determine if magnetic torques can spin down massive stars during their formation. I found that magnetic torques are insufficient to spin down massive stars due to their short formation times and high accretion rates. Radiation pressure is likely the dominate feedback mechanism regulating massive star formation. Therefore detailed simulation of the formation of massive stars requires an accurate treatment of radiation. For this purpose, I developed a new, highly accurate radiation algorithm that properly treats the absorption of the direct radiation field from stars and the re-emission and processing by interstellar dust. With this new tool, I performed a suite of three-dimensional adaptive mesh refinement radiation-hydrodynamic simulations of the formation of massive stars from collapsing massive pre-stellar cores. I found that mass is channeled to the massive star via dense infalling filaments that are uninhibited by radiation pressure and gravitational and Rayleigh-Taylor instabilities. To determine the importance of stellar wind feedback in young MSCs, I used observations to constrain a range of kinetic energy loss channels for the hot gas produced by the shock-heating of stellar winds to explain the low X-ray luminosities observed in Hii regions. I demonstrated that the energy injected by stellar winds is not a significant contributor to stellar feedback in young MSCs.
