Search results for: from-the-realm-of-the-nebulae-to-populations-of-galaxies

From the Realm of the Nebulae to Populations of Galaxies

Author : Mauro D'Onofrio
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In order to outline possible future directions in galaxy research, this book wants to be a short stopover, a moment of self-reflection of the past century of achievements in this area. Since the pioneering years of galaxy research in the early 20th century, the research on galaxies has seen a relentless advance directly connected to the parallel exponential growth of new technologies. Through a series of interviews with distinguished astronomers the editors provide a snapshot of the achievements obtained in understanding galaxies. While many initial questions about their nature have been addressed, many are still open and require new efforts to achieve a solution. The discussions may reveal paradigms worthwhile revisiting. With the help of some of those scientists who have contributed to it, the editors sketch the history of this scientific journey and ask them for inspirations for future directions of galaxy research.

The Realm of the Nebulae

Author : Edwin Powell Hubble
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No modern astronomer made a more profound contribution to our understanding of the cosmos than did Edwin Hubble, who first conclusively demonstrated that the universe is expanding. Basing his theory on the observation of the change in distanct galaxies, called red shift, Hubble showed that this is a Doppler effect, or alteration in the wavelength of light, resulting from the rapid motion of celestial objects away from Earth. In 1935, Hubble described his principal observations and conclusions in the Silliman lectures at Yale University. These lectures were published the following year as "The Realm of the Nebulae," which quickly became a classic work.

The Encyclopedia Americana

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A Multifaceted Perspective on Galaxy Evolution

Author : Tim Haines
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A key component of astronomy is the study of how galaxies change over time. Once thought to be static "island universes" today, we know that galaxies are dynamic systems reacting to changes in their internal and external environments in myriad ways. From simple observables like their shapes and colors to the complex interplay of their intricate stellar populations, evolving galaxies contain a wealth of information about their past. Yet, these observables alone are not enough to allow us to determine how these galaxies came to be or what they will become. For that, we need to combine theoretical models assembled from fundamental laboratory physics and apply them to galaxies through the use of state- of-the-art computer simulations. This careful combination of observation and computation has allowed our understanding of galaxy evolution to transition from the simple realm of the nebulae into a substantial field of astronomy. In this thesis, we explore three perspectives of galaxy evolution at different levels of detail- through both observations and computer simulations. We begin with a simple observation: the stars in our galaxy appear to be moving in strange ways. If our Galaxy were living an uneventful life, we would expect all of the stars to be moving in nearly circular orbits with small, but appreciable, vertical motions- much like the horse on a carousel. However, recent surveys of nearby stars have found substantial deviations from such a perfect life. With the stars moving vertically in ways that indicate the galaxy has been rung like a bell. Some observers have posited that interactions with very nearby galaxies like the Sagittarius dwarf may be responsible for these unusual stellar motions. In Chapter 2, we use a simulated version of the Milky Way that is undergoing an interaction with a small companion galaxy to explore how such an interaction can affect the motions of stars near the Sun and what effect this may have on the nearly century-old ii problem known as the Oort Limit. Our own galaxy is but one example of an entire population disk-like galaxies with blue colors due to the presence of newly-formed stars. Opposite this population of "blue cloud" galaxies is the "red sequence" which is made up of spheroidal galaxies with red colors due to having nearly no ongoing star formation. In Chapter 3, we take a detailed look at an exceptionally rare, but quite important subpopulation of galaxies that are thought to be transitioning between the blue cloud and the red sequence through the so-called "green valley." Much like transitional fossils in biology, these galaxies have properties intermediate between both the disk-like galaxies of the blue cloud and the massive spheroids of the red sequence. Although few in number, the presence in the universe provides us with a critical view of the fleeting transitions these galaxies are undergoing to help us unlock the mysteries of how massive galaxies in the universe form. Our understanding of galaxy evolution at every scale relies heavily on computer simulations. In Chapter 4, we approach the subject through the lens of a software developer writing a modern N-body solver used to simulate the gravitational dynamics of galaxies. In particular, we explore how utilizing accelerator hardware like graphics processing units (GPUs) can increase both the precision and size of problems that can be solved in galaxy evolution both for today and tomorrow.

Stellar Populations

Author : Piet C. van der Kruit
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The concept of Stellar Populations has played a fundamental role in astronomy in the last few decades. It was introduced by Walter Baade after he was able to resolve the Andromeda Nebula and its companions into stars when he used red-sensitive plates and realised that there were two fundamentally different Herzsprung-Russell diagrams in our and these nearby galaxies (common stars in the solar neighborhood versus globular clusters). This result was published in two papers in 1944 in volume 100 of the Astrophysical Journal. Subsequent research gave the concept a much firmer basis and at the famous Vatican Symposium of 1957 resulted in a general scheme of the concept and a working hypothesis for idea's on the formation and evolution of the Galaxy. This has been a guiding principle of studies of our and other galaxies for decades. Some years ago it seemed to us appropriate to commemorate Baade's seminal work in 1994, when it would have its 50-th anniversary, and to review its present status and also its role in contempory understanding. While we were in Leiden for an administrative committee, we discussed the matter again and over beers on October 29, 1991 we decided the take the initiative for an IAU Symposium on the subject during the 1994 IAU General Assembly in Den Haag, the Netherlands.

Quasars at All Cosmic Epochs

Author : Paola Marziani
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The last 50 years have seen a tremendous progress in the research on quasars. From a time when quasars were unforeseen oddities, we have come to a view that considers quasars as active galactic nuclei, with nuclear activity a coming-of-age experienced by most or all galaxies in their evolution. We have passed from a few tens of known quasars of the early 1970s to the 500,000 listed in the catalogue of the Data Release 14 of the Sloan Digital Sky Survey. Not surprisingly, accretion processes on the central black holes in the nuclei of galaxies — the key concept in our understanding of quasars and active nuclei in general — have gained an outstanding status in present-day astrophysics. Accretion produces a rich spectrum of phenomena in all bands of the electromagnetic spectrum. The power output of highly-accreting quasars has impressive effects on their host galaxies. All the improvement in telescope light gathering and in computing power notwithstanding, we still miss a clear connection between observational properties and theory for quasars, as provided, for example, by the H-R diagram for stars. We do not yet have a complete self-consistent view of nuclear activity with predictive power, as we do for main-sequence stellar sources. At the same time quasars offer many “windows open onto the unknown". On small scales, quasar properties depend on phenomena very close to the black hole event horizon. On large scales, quasars may effect evolution of host galaxies and their circum-galactic environments. Quasars’ potential to map the matter density of the Universe and help reconstruct the Universe’s spacetime geometry is still largely unexploited. The times are ripe for a critical assessment of our present knowledge of quasars as accreting black holes and of their evolution across the cosmic time. The foremost aim of this research topic is to review and contextualize the main observational scenarios following an empirical approach, to present and discuss the accretion scenario, and then to analyze how a closer connection between theory and observation can be achieved, identifying those aspects of our understanding that are still on a shaky terrain and are therefore uncertain knowledge. This research topic covers topics ranging from the nearest environment of the black hole, to the environment of the host galaxies of active nuclei, and to the quasars as markers of the large scale structure and of the geometry of spacetime of the Universe. The spatial domains encompass the accretion disk, the emission and absorption regions, circum-nuclear starbursts, the host galaxy and its interaction with other galaxies. Systematic attention is devoted to some key problems that remain outstanding and are clearly not yet solved: the existence of two quasar classes, radio quiet and radio loud, and in general, the systematic contextualization of quasar properties the properties of the central black hole, the dynamics of the accretion flow in the inner parsecs and the origin of the accretion matter, the quasars’ small and large scale environment, the feedback processes produced by the black hole into the host galaxy, quasar evolutionary patterns from seed black holes to the present-day Universe, and the use of quasars as cosmological standard candles. The timing is appropriate as we are now witnessing a growing body of results from major surveys in the optical, UV X, near and far IR, and radio spectral domains. Radio instrumentation has been upgraded to linear detector — a change that resembles the introduction of CCDs for optical astronomy — making it possible to study radio-quiet quasars at radio frequencies. Herschel and ALMA are especially suited to study the circum-nuclear star formation processes. The new generation of 3D magnetohydrodynamical models offers the prospective of a full physical modeling of the whole quasar emitting regions. At the same time, on the forefront of optical astronomy, applications of adaptive optics to long-slit spectroscopy is yielding unprecedented results on high redshift quasars. Other measurement techniques like 2D and photometric reverberation mapping are also yielding an unprecedented amount of data thanks to dedicated experiments and instruments. Thanks to the instrumental advances, ever growing computing power as well as the coming of age of statistical and analysis techniques, the smallest spatial scales are being probed at unprecedented resolution for wide samples of quasars. On large scales, feedback processes are going out of the realm of single-object studies and are entering into the domain of issues involving efficiency and prevalence over a broad range of cosmic epochs. The Research Topic "Quasars at all Cosmic Epochs" collects a large fraction of the contributions presented at a meeting held in Padova, sponsored jointly by the National Institute for Astrophysics, the Padova Astronomical Observatory, the Department of Physics and Astronomy of the University of Padova, and the Instito de Astrofísica de Andalucía (IAA) of the Consejo Superiór de Investigación Cientifica (CSIC). The meeting has been part of the events meant to celebrate the 250th anniversary of the foundation of the Padova Observatory.

Karl Popper s Science and Philosophy

Author : Zuzana Parusniková
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Physics of Nearby Galaxies

Author : Xuan Thuan Trinh
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Galaxy Formation

Author : Malcolm S. Longair
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Written by a well-known astrophysicist, who is also a superbly talented writer, this work deals with the matter and radiation content of the universe, the formation of galaxies, and provides a comprehensive introduction into relativistic astrophysics as needed for the clarification of cosmological ideas.

Morphological Astronomy

Author : Fritz Zwicky
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Man has a great tendency to get lost or to hide, as the case may be, in a jungle of details and in unnecessary complications. Why do anything simply if you can do it complicated? And still, life itself presents a sufficient number of problems to keep us busy. There would seem to be no need to create additional difficulties, just for the fun of it, especially if these self-made difficulties become practically insuperable and if in the end they cause much unhappiness. The morphological mode of thought and of action was conceived to break the vicious hold which the parasitic wild growth of complications exerts on life in all of its phases. Morphological thought and action are likely to be of value in all human activities, once such thought and action have been clearly delineated and fully developed, and once they have been practised by a sufficiently large number of people. Since the morphological method is of the greatest universality, the choice of the field to which one applies it first is not particulary critical. The author intends to write two or three books on the morphology of several large scale problems, which are both of a technical and of a general social nature. The present book is concerned in particular with some implications of morphological thinking in astronomy. We shall above all emphasize the basic character of the morphological approach, and we shall demonstrate its constructive power in a number of specific cases.

Cosmic Odyssey

Author : Linda Schweizer
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"Stories of 20th century astronomers working at the frontiers of astrophysics whose discoveries on the Palomar telescopes shattered and expanded our view of the universe"--

Lyman Alpha Emitting Galaxies at High Redshift

Author : Steven Arthur Dawson
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As late as 1995, the anticipated widespread population of primeval galaxies remained at large, lurking undetected at unknown redshifts, with undiscovered properties. We present results from our efforts to detect and characterize primeval galaxies by their signature high-redshift Lyman-alpha emission lines utilizing two observational techniques: serendipitous slit spectroscopy and narrowband imaging. By pushing these techniques to their utmost limits, we probe the Lyman-alpha-emitting galaxy population out to redshifts as high as z = 6.5. Galaxies at this epoch reside in a universe which is just 800 million years old, a mere 6% of its current age. As such, this work provides one account of the manner by which observational cosmology has recently shifted from merely marveling at the incredible lookback times implied by the first few high-redshift detections, to the routine assembly of high-redshift datasets designed to address specific astrophysical issues.

The Spiral Structure of Our Galaxy

Author : W. Becker
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The idea of the organization of a Symposium on Spiral Structure came at a special meeting of Commission 33 on Spiral Structure during the 12th General Assembly of the IAU in Prague, 1967. So much interest was shown during this meeting that one of us proposed a special Symposium on the 'Spiral Structure of Our Galaxy' for 1969. The response was immediate and it was finally agreed upon holding the Symposium in Basel, a center of galactic research in the center of Europe. During the next months a special 'List of Problems', related to this Symposium, was sent to many prospective participants by the president of Commission 33. This stimulated an increase of interest in problems of galactic spiral structure and a con centrated effort on some problems. The organizing Committee of the Symposium was composed of Drs. L. Woltjer (president), W. Becker, A. Blaauw, B. J. Bok, G. Contopoulos, F. J. Kerr, C. C. Lin, S. W. McCuskey and S. B. Pikel'ner. Most of the work for the organization of the Symposium was carried by Dr. L. W oltjer. The Local Committee, composed of Drs. W. Becker, U. W. Steinlin, R. P. Fenkart, and G. A. Tammann, made every effort to secure the success of the Symposium. Most of the credit goes to Dr. Steinlin. The Symposium was supported financially by the IAU and by the Swiss National Science Foundation. The meetings took place at the University of Basel, which provided also secretarial help and many other facilities.

Penetrating Bars through Masks of Cosmic Dust

Author : David L. Block
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THE EDITORS: DAVID L. BLOCK AND KENNETH C. FREEMAN (SOC CO-CHAIRS), IVANIO PUERARI, ROBERT GROESS AND LIZ K. BLOCK 1. Harvard College Observatory, 1958 The past century has truly brought about an explosive period of growth and discovery for the physical sciences as a whole, and for astronomy in particular. Galaxy morphology has reached a renaissance . . The year: 1958. The date: October 1. The venue: Harvard College Observatory. The lecturer: Walter Baade. With amazing foresight, Baade penned these words: "Young stars, supergiants and so on, make a terrific splash - lots of light. The total mass of these can be very small compared to the total mass of the system". Dr Layzer then asked the key question: " . . . the discussion raises the point of what this classification would look like if you were to ignore completely all the Population I, and just focus attention on the Population II . . . " We stand on the shoulders of giants. The great observer E. E. Barnard, in his pioneering efforts to photograph the Milky Way, devoted the major part of his life to identifying and numbering dusty "holes" and dust lanes in our Milky Way. No one could have dreamt that the pervasiveness of these cosmic dust masks (not only in our Galaxy but also in galaxies at high redshift) is so great, that their "penetration" is truly one of the pioneering challenges from both space-borne telescopes and from the ground.

Edwin Hubble The Discoverer of the Big Bang Universe

Author : Alexander S. Sharov
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This book is the first complete account of the scientific life and work of Edwin Hubble, whose discoveries firmly established the United States as the leading nation in observational astronomy. One of the outstanding astronomers of the twentieth century, Hubble discovered the expansion of the Universe. He opened the world of galaxies for science when he showed that spiral nebulae beyond the Milky Way are galaxies extending to the limits of the Universe, and participating in a general expansion of the cosmos. The exploding Universe of Hubble, now termed the Big Bang, determined the origin of the elements, of galaxies and of the stars. The second part of the book describes the fundamental discoveries on the nature of the Universe made subsequently, and thus sets his achievements in context. Written by two prominent astronomers who have built on Hubble's work, this book is a classic of science, setting out the thrilling story of the exploding Universe.

Dynamics and Interactions of Galaxies

Author : Roland Wielen
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Progress towards an understanding of the dynamics and interactions of galaxies has been spurred on more than ever by a wealth of new observations and numerical experiments. The Heidelberg Conference 1989, the papers of which are collected in this volume, was extremely successful in presenting a synoptic view of the field in all its aspects: galaxy interactions in the early universe and in recent times, interactions of our galaxy and its neighbours, dynamical problems of elliptical and disk galaxies, groups and clusters, starburst and nuclear activity triggered by interactions, merger scenarios, and numerical experiments. Researchers and graduate students, specialists or not, will find here a complete overview of a rapidly growing field of astronomy.

Changing Views of the Physical World 1954 1979

Author : Guy Kendall White
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Galaxy Interactions at Low and High Redshift

Author : International Astronomical Union. Symposium
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Proceedings of the 186th Symposium of the International Astronomical Union, held at Kyoto, Japan, 26-30 August 1997

The Distribution of the Galaxies

Author : William C. Saslaw
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It embeds distribution functions in a broader astronomical context, including other exciting contemporary topics such as correlation functions, fractals, bound clusters, topology, percolation, and minimal spanning trees."--BOOK JACKET. "This volume is written at a level suitable for graduate students and will be of key interest to astronomers, cosmologists, physicists, and applied statisticians."--BOOK JACKET.