Download or read book Understanding Spatial and Spectral Morphologies of Ultracompact H II Regions written by and published by . This book was released on 2010 with total page 15 pages. Available in PDF, EPUB and Kindle. Book excerpt: The spatial morphology, spectral characteristics, and time variability of ultracompact H II regions provide strong constraints on the process of massive star formation. We have performed simulations of the gravitational collapse of rotating molecular cloud cores, including treatments of the propagation of ionizing and non-ionizing radiation. We here present synthetic radio continuum observations of H II regions from our collapse simulations, to investigate how well they agree with observation, and what we can learn about how massive star formation proceeds. We find that intermittent shielding by dense filaments in the gravitationally unstable accretion flow around the massive star leads to highly variable H II regions that do not grow monotonically, but rather flicker, growing and shrinking repeatedly. This behavior appears able to resolve the well-known lifetime problem. We find that multiple ionizing sources generally form, resulting in groups of ultracompact H II regions, consistent with observations. We confirm that our model reproduces the qualitative H II region morphologies found in surveys, with generally consistent relative frequencies. We also find that simulated spectral energy distributions (SEDs) from our model are consistent with the range of observed H II region SEDs, including both regions showing a normal transition from optically thick to optically thin emission, and those with intermediate spectral slopes. In our models, anomalous slopes are solely produced by inhomogeneities in the H II region, with no contribution from dust emission at millimeter or submillimeter wavelengths. We conclude that many observed characteristics of ultracompact H II regions appear consistent with massive star formation in fast, gravitationally unstable, accretion flows.
Download or read book Ultracompact HII Regions written by Edward B. Churchwell and published by . This book was released on 1987 with total page 19 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Morphologies and Physical Properties of Ultracompact HII Regions written by Douglas O. S. Wood and published by . This book was released on 1988 with total page 65 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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 Formation Of The First Black Holes written by Muhammad Latif and published by World Scientific. This book was released on 2019-04-26 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt: The formation of the first supermassive black holes is one of the main open questions in our understanding of high-redshift structure formation. In this book, we aim to provide a summary of state-of-the-art modern research on this topic, exploring the formation of massive black holes from a fluid-dynamical, stellar-dynamical and chemical perspective. The book thus presents a solid theoretical foundation, a comparison with current observations and future observational perspectives with upcoming missions such as the Square Kilometre Array, the European Extremely Large Telescope, the Euclid satellite as well as possible detections via gravitational waves.
Download or read book The Physics and Chemistry of the Interstellar Medium written by A. G. G. M. Tielens and published by Cambridge University Press. This book was released on 2005-08-25 with total page 522 pages. Available in PDF, EPUB and Kindle. Book excerpt: This work provides a comprehensive overview of our theoretical and observational understanding of the interstellar medium of galaxies. With emphasis on the microscopic physical and chemical processes in space, and their influence on the macroscopic structure of the interstellar medium of galaxies, the book includes developments in this area of molecular astrophysics. The various heating, cooling, and chemical processes relevant for the rarefied gas and submicron-sized dust grains that constitute the interstellar medium are discussed in detail. This provides a firm foundation for an in-depth understanding of the ionized, neutral atomic, and molecular phases of the interstellar medium. The physical and chemical properties of large polycyclic aromatic hydrocarbon molecules and their role in the interstellar medium are highlighted, and the physics and chemistry of warm and dense photodissociation regions are discussed. This is an invaluable reference source for advanced undergraduate and graduate students, and research scientists.
Download or read book Stellar populations as building blocks of galaxies proceedings of the 241th symposium of the International Astronomical Union held in La Palma Tenerife Spain December 10 16 2006 written by International Astronomical Union. Symposium and published by Cambridge University Press. This book was released on 2007 with total page 628 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physical Processes in the Interstellar Medium written by Lyman Spitzer, Jr. and published by John Wiley & Sons. This book was released on 2008-11-20 with total page 335 pages. Available in PDF, EPUB and Kindle. Book excerpt: Physical Processes in the Interstellar Medium discusses the nature of interstellar matter, with a strong emphasis on basic physical principles, and summarizes the present state of knowledge about the interstellar medium by providing the latest observational data. Physics and chemistry of the interstellar medium are treated, with frequent references to observational results. The overall equilibrium and dynamical state of the interstellar gas are described, with discussions of explosions produced by star birth and star death and the initial phases of cloud collapse leading to star formation.
Download or read book New Catalogs of Radio Compact H II Regions in the Milky Way written by Uriel Giveon and published by . This book was released on 2005 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt:
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.
Download or read book Ultracompact HII Regions written by Edward B. Churchwell and published by . This book was released on 1990 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Circumstellar Matter 1994 written by Graeme D. Watt and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 608 pages. Available in PDF, EPUB and Kindle. Book excerpt: The conference recorded in this volume was one of the events organised to celebrate the centenary of the (re)establishment of the Royal Observatory, Edinburgh, on Blackford Hill in 1884. Circumstellar Matter was selected as the topic because of important contributions toward research in the field by recent observations in the infrared and submillimetre, particularly with the two telescopes which the Observatory has both operated and built instru mentation for - the United Kingdom Infrared Telescope (UKIRT) and the James Clerk Maxwell Telescope (JCMT). The programme aimed to cover as many aspects of circumstellar matter as could fit into a one-week meeting, omitting only planetary nebulae, which had been well served by meetings in the previous two years. We thank the international scientific advisory com mittee (overleaf) for their help in selecting the Invited Reviewers around which the programme was built. The Invited Reviews and oral contributions are included in the order and sections in which they were presented, even where re-ordering might have been more logical. We did not attempt to categorise the poster contributions but have included them in alphabetical order. An evening session for viewing and discussing posters in an unhurried atmosphere was very successful. A competition for the best poster was held and the prize was awarded for that by Lindqvist, Lucas, Olofsson, Omont, Eriksson & Gustafsson.
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 Flux Densities of Ultracompact H II Regions at 3 MM written by Douglas O. S. Wood and published by . This book was released on 1987 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Literature 1985 Part 2 written by S. Böhme and published by Springer Science & Business Media. This book was released on 2013-12-14 with total page 1106 pages. Available in PDF, EPUB and Kindle. Book excerpt: Astronomy and Astrophysics Abstracts aims to present a comprehensive documen tation ofthe literatme concerning all aspects of astronomy, astrophysics, and their border fields. lt is devoted to the recording, summarizing, and indexing of the relevant publications throughout the world. Astronomy and Astrophysics Abstracts is prepared by a special department of the Astronomisches Rechen-Institut under the auspices of the International Astronomical Union. Volume 40 records literatme published in 1985 and received before February 15, 1986. Some older documents which we received late and which arenot surveyed in earlier volumes are included too. We acknowledge with thanks contributions of our colleagues all over the world. We also express our gratitude to all organiza tions, observatories, and publishers which provide us with complimentary copies of their publications. Starting with Volume 33, all the recording, correction, and data processing work was dorre by means of computers. The recording was dorre by om technical staff members Ms. Helga Ballmann, Ms. Mona El-Choura (t), Ms. Monika Kohl, Ms. Sylvia Matyssek. Ms. Karirr Burkhardt, Ms. Susanne Schlötelbmg, Mr. Mar tin Schlötelburg, and Mr. Stefan Wagner supported om task by careful proof reading. lt is a pleasure to thank them all for their encomagement.
Download or read book Radio Recombination Lines 25 Years of Investigation written by M.A. Gordon and published by Springer Science & Business Media. This book was released on 2012-12-06 with total page 295 pages. Available in PDF, EPUB and Kindle. Book excerpt: Text no 1 Radio Recombination Lines (RRLs), discovered in the USSR in 1964, have become a powerful research tool for astronomers. Available throughout the radio spectrum, these lines carry information regarding the density, temperature, turbulence and velocity of thermal plasmas. Their very existance shows the presence of thermal gas. They also can carry information regarding magnetic fields if Zeeman splitting were to be detected. Containing the proceedings of an IAU Colloquium celebrating the 25th anniversary of their detection, this volume tells us what has happened since. It contains the story of the detection of RRLs and reviews of many areas of physics of the interstellargas from which stars form, HII regions excited by newly formed stars, planetary nebulae involving dying stars, and the structure of our Milky Way and other galaxies reflecting the large-scale morphology of the star formation process. In addition there is an article describing modern laboratory studies of Rydberg atoms to probe the basic physics of atomic structure, and articles describing the theory of collisions and radiation upon Rydberg atoms leading to observate effects to be used as diagnostic tools in astromony. This book focuses on the 25 years of astronomical research with radio recombination lines (RRLs) since their discovery in 1965. It covers a wide range of topics: papers dealing with research into Rydberg atoms both in the laboratory and in the interstellar medium of our galaxy and others; papers on the interaction of radiation and atomic systems, as well as with the effects of inadiabatic collisions between these atoms and both ions and electrons. It deals with astronomical observations of atoms with `diameters' ranging from 0.08 to 50 mum a size factor of 625. It deals with RRLs in absorption, in emission and as true masers. And it deals with plasmas with temperatures ranging from 10 to greater than 104 kelvins, and with an even greater range of volume densities. Much new work is reported, including low frequency RRLs discovered in 1980 and the maser RRLs from the star MWC349, discovered in 1989. The advent of aperture synthesis telescopes and large single-element telescopes have made possible RRL studies with high angular resolution. The sum total of the work reported here will make the volume a platform from which to search new horizons in RRL research.
