Download or read book Stellar Disk Evolution and Gaseous Disk Turbulence of Dwarf Irregular Galaxies written by Hong-Xin Zhang and published by Springer. This book was released on 2016-08-27 with total page 179 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book focuses on the stellar disk evolution and gas disk turbulence of the most numerous galaxies in the local Universe – the dwarf galaxies. The “outside-in” disk shrinking mode was established for a relatively large sample of dwarf galaxies for the first time, and this is in contrast to the “inside-out” disk growth mode found for spiral galaxies. Double exponential brightness profiles also correspond to double exponential stellar mass profiles for dwarf galaxies, which is again different from most spiral galaxies. The cool gas distribution in dwarf galaxies was probed with the spatial power spectra of hydrogen iodide (HI) gas emission, and provided indirect evidence that inner disks of dwarf galaxies have proportionally more cool gas than outer disks. The finding that no correlation exists between gas power spectral indices and star formation gave important constraints on the relation between turbulence and star formation in dwarf galaxies.
Download or read book Island Universes written by R. S. de Jong and published by Springer. This book was released on 2006-12-15 with total page 582 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book contains an up-to-date review of the structure and evolution of disk galaxies from both the observational and theoretical point of view. It is the proceedings of the "Island Universes" conference held at the island of Terschelling in July 2005. It brings together a broad range of aspects of disk galaxies: structure and dynamics, the latest multi-wavelength surveys, low- and high redshift observations, theory and observations.
Download or read book Star forming Dwarf Galaxies and Related Objects written by D. Kunth and published by Atlantica Séguier Frontières. This book was released on 1985 with total page 540 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Dynamical Evolution of Disk Galaxies written by Frank Hohl and published by . This book was released on 1970 with total page 116 pages. Available in PDF, EPUB and Kindle. Book excerpt: A computer model for isolated disks of stars is presented and is used to study the self-consistent motion of large numbers of point masses as they move in the plane of the galactic disk. The Control Data 6600 computer system at the Langley Research Center was used to integrate the equations of motion for each star for systems containing from 50,000 to 200,000 stars. Any initially cold balanced disk was found to be violently unstable. A sufficient amount of velocity dispersion will stabilize all small-scale disturbances. However, most disks investigated were found to be unstable against slowly growing long-wavelength modes, and after about two rotations the disks tended to assume a bar-shaped structure. It was also found that the final mass distribution for most disks could be closely approximated by an exponential variation irrespective of the initial mass distribution. To study the development of spiral structure, the model was modified to include a fixed central force similar to that in the Schmidt model of the Galaxy. The mass of the stars in the disk was taken to be from 5 to 50 percent of the total mass of the Galaxy. The evolution of a number of initial distributions of stars was investigated. The results of the calculation gave a velocity dispersion for the disk stars which was about 50 percent larger than the value of about 30 km/sec found from observation of stars in the solar neighborhood. For some of the disks investigated, a pronounced spiral structure remained even after 8.5 rotations.
Download or read book Dynamical Evolution of Galaxies written by Xiaolei Zhang and published by Walter de Gruyter GmbH & Co KG. This book was released on 2017-12-04 with total page 421 pages. Available in PDF, EPUB and Kindle. Book excerpt: This research monograph presents a new dynamical framework for the study of secular morphological evolution of galaxies along the Hubble sequence. Classical approaches based on Boltzmann’s kinetic equation, as well as on its moment-equation descendants the Euler and Navier-Stokes fluid equations, are inadequate for treating the maintenance and long-term evolution of systems containing self-organized structures such as galactic density-wave modes. A global and synthetic approach, incorporating correlated fluctuations of the constituent particles during a nonequilibrium phase transition, is adopted to supplement the continuum treatment. The cutting-edge research combining analytical, N-body simulational, and observational aspects, as well as the fundamental-physics connections it provides, make this work a valuable reference for researchers and graduate students in astronomy, astrophysics, cosmology, many-body physics, complexity theory, and other related fields. Contents Dynamical Drivers of Galaxy Evolution N-Body Simulations of Galaxy Evolution Astrophysical Implications of the Dynamical Theory Putting It All Together Concluding Remarks Appendix: Relation to Kinetics and Fluid Mechanics
Download or read book The Stellar Content and Star Formation Rates of Dwarf Irregular Galaxies written by Jacqueline Michelle Dunn and published by . This book was released on 2007 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The star formation histories and evolution of 70 dwarf irregular galaxies that reside in differing local and global environments are investigated. Local environment is defined by the local galaxy number density, where high indicates at least one neighbor within 200 kpc and low indicates no neighbors within 1 Mpc. Global environment is classified as either the field or a galaxy group / cluster. The shallow gravitational potentials of these galaxies are more susceptible to changes in morphology and dynamics by external perturbations, making dwarf irregular galaxies ideal candidates for a study on the role of environment in galaxy evolution. Absolute magnitudes, colors, central surface brightnesses, and star formation rates were compared using UBVRIJHK and Halpha photometry. With a high degree of statistical significance, galaxies in local high density environments have brighter central and effective surface brightnesses, while those in global high density environments have brighter absolute magnitudes, central and effective surface brightnesses, and higher star formation rates. However, no difference is seen among the different environments when considering star formation rates normalized by HI mass. Sersic profiles were fit to the V and R band surface brightness profiles of the galaxies. No correlation exists between structural characteristics and environment. Spectral energy distribution models were generated by varying the rate of stellar formation and amplitude to replicate periodic burst and constant star formation rate scenarios. Of the 28 galaxies for which star formation history analysis was performed, roughly half were well fit by one of the models. Periodic burst systems account for roughly half of those galaxies, with the remaining galaxies being better represented by continuously star forming systems. The star formation histories are uncorrelated with both local and global environmental classifications. Numerical simulations provide insight into the effects of differing gravitational environments, and indicate global environment having a larger influence on the physical properties of a dwarf galaxy. The star formation histories and structural properties of dwarf irregular galaxies were found to be independent of environment, indicating that cluster membership and proximity to a neighboring galaxy have no systematic long-term effects on the evolution of the objects in this study.
Download or read book High Angular Resolution Studies of the Structure and Evolution of Protoplanetary Disks written by Joshua Eisner and published by Universal-Publishers. This book was released on 2005 with total page 240 pages. Available in PDF, EPUB and Kindle. Book excerpt: Young stars are surrounded by massive, rotating disks of dust and gas, which supply a reservoir of material that may be incorporated into planets or accreted onto the central star. In this dissertation, I use high angular resolution observations at a range of wavelengths to understand the structure, ubiquity, and evolutionary timescales of protoplanetary disks. First, I describe a study of Class I protostars, objects believed to be at an evolutionary stage between collapsing spherical clouds and fully-assembled young stars surrounded by protoplanetary disks. I use a Monte Carlo radiative transfer code to model new 0.9 micron scattered light images, 1.3 mm continuum images, and broadband spectral energy distributions. This modeling shows that Class I sources are probably surrounded by massive protoplanetary disks embedded in massive infalling envelopes. For the best-fitting models of the circumstellar dust distributions, I determine several important properties, including envelope and disk masses, mass infall rates, and system inclinations, and I use these results to constrain the evolutionary stage of these objects. Second, I discuss observations of the innermost regions of more evolved disks around T Tauri and Herbig Ae/Be stars, obtained with the Palomar Testbed and Keck Interferometers. I constrain the spatial and temperature structure of the circumstellar material at sub-AU radii, and demonstrate that lower-mass stars are surrounded by inclined disks with puffed-up inner edges 0.1-1 AU from the star. In contrast, the truncated inner disks around more massive stars may not puff-up, indicating that disk structure depends on stellar properties. I discuss the implications of these results for disk accretion, terrestrial planet formation and giant planet migration. Finally, I put these detailed studies of disk structure into a broader context by constraining the mass distribution and evolutionary timescales of circumstellar disks. Using the Owens Valley Millimeter Array, I mapped the millimeter continuum emission toward >300 low-mass stars in the NGC 2024 and Orion Nebula clusters. These observations demonstrate that the average disk mass in each cluster is comparable to the "minimum-mass protosolar nebula," and that there may be disk evolution on one million year timescales.
Download or read book Physical Processes in Circumstellar Disks around Young Stars written by Paulo J. V. Garcia and published by University of Chicago Press. This book was released on 2011-04-15 with total page 437 pages. Available in PDF, EPUB and Kindle. Book excerpt: Circumstellar disks are vast expanses of dust that form around new stars in the earliest stages of their birth. Predicted by astronomers as early as the eighteenth century, they weren’t observed until the late twentieth century, when interstellar imaging technology enabled us to see nascent stars hundreds of light years away. Since then, circumstellar disks have become an area of intense study among astrophysicists, largely because they are thought to be the forerunners of planetary systems like our own—the possible birthplaces of planets. This volume brings together a team of leading experts to distill the most up-to-date knowledge of circumstellar disks into a clear introductory volume. Understanding circumstellar disks requires a broad range of scientific knowledge, including chemical processes, the properties of dust and gases, hydrodynamics and magnetohydrodynamics, radiation transfer, and stellar evolution—all of which are covered in this comprehensive work, which will be indispensable for graduate students, seasoned researchers, or even advanced undergrads setting out on the study of planetary evolution.
Download or read book Lessons from the Local Group written by Kenneth Freeman and published by Springer. This book was released on 2014-11-13 with total page 510 pages. Available in PDF, EPUB and Kindle. Book excerpt: Our understanding of galaxy formation comes mostly from two sources: sensitive observations at high angular resolution of the high-redshift Universe, where galaxies are observed to be forming, and detailed observations of individual stars and clouds in the Local Group, where telltale remnants from its formative time remain and similar processes operate at a low level today. The current conference focusses on key aspects of the Local Group, composed of the Milky Way, Andromeda and Triangulum Spiral Galaxies, the Large and Small Magellanic Cloud galaxies, numerous dwarf and irregular galaxies, and intergalactic gas. Topics include the halo and thick disk of the Milky Way with its first stars and stellar streams; the Milky Way bar, bulge and outer edge; interstellar dust and turbulence; star formation processes and stellar scattering in spiral arms; views through the infrared Eyes of the Spitzer Space Telescope; globular clusters; the Local Gould Belt; stellar metallicities and elemental abundances; the environment and black hole in the Milky Way nucleus; orbits of the Magellanic Clouds and galaxy dwarfs; interstellar dust and turbulence; the outer disks and halos of the Andromeda and Triangulum galaxies; ripples from a collision in Andromeda; and arcs of carbon stars in the Triangulum and intergalactic clouds. This volume also discusses surveys of planetary nebulae, galaxy morphology at low and high redshift, cosmic evolution of star and galaxy formation and gas accretion, Lyman alpha emitting galaxies, ultra-low surface brightness imaging, and more. Readers are given a clear and comprehensive view of this wide range of topics written by specialists in each field. This is the proceedings of an International Conference at the Seychelles archipelago in May 2014, on the occasion of the 60th birthday of David Block and the millionth (base two) birthday of Bruce Elmegreen.
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 Introduction to Galaxy Formation and Evolution written by Andrea Cimatti and published by . This book was released on 2019-10-31 with total page 588 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive examination of nearly fourteen billion years of galaxy formation and evolution, from primordial gas to present-day galaxies.
Download or read book Accretion Disks In Compact Stellar Systems written by J Craig Wheeler and published by World Scientific. This book was released on 1993-12-22 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: Accretion disks in compact stellar systems containing white dwarfs, neutron stars or black holes are the principal laboratory for understanding the role of accretion disks in a wide variety of environments from proto-stars to quasars. Recent work on disk instabilities and dynamics has given a new theoretical framework with which to study accretion disks. Modeling of time-dependent phenomena provides new insight into the causes and interpretation of photometric and spectroscopic variability and new constraints on the fundamental physical problem — the origin of viscosity in accretion disks. This book contains expert reviews on the nature of limit cycle thermal instabilities and a variety of closely related topics from the theory of angular momentum transport to eclipse mapping of the disk structure. The result is a comprehensive contemporary survey of the structure and evolution of accretion disks in compact binary systems.
Download or read book The Galaxy Disk in Cosmological Context IAU S254 written by International Astronomical Union. Symposium and published by Cambridge University Press. This book was released on 2009-04-16 with total page 542 pages. Available in PDF, EPUB and Kindle. Book excerpt: The paradigm of a dark energy- and dark matter-dominated Universe, with the hierarchical merger scenario for the formation of galaxies, has scored impressive successes in matching the observed Universe. However, the theory fails to explain the difficulty in generating ordinary disk galaxies such as the Milky Way, suggesting that some important physics must be missing in current models. IAU Symposium 254 was organized to address this question, gathering researchers from an unusually broad range of fields, from cosmology to interstellar matter, and the formation and evolution of stars. High-class reviews, lectures and posters combine to define the frontiers in the field and point the way to new avenues of research. This volume presents a unique set of succinct overviews illuminating the full range of topics in this very active field. It also honors Danish astrophysicist Bengt Strömgren (1908-1987), who laid much of the foundation for this entire field.
Download or read book Molecular Gas in Dwarf Galaxies written by Adam Kirby Leroy and published by . This book was released on 2006 with total page 578 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Physics of the Gaseous and Stellar Disks of the Galaxy written by Ivan R. King and published by . This book was released on 1994 with total page 376 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Chemical Evolution of Dwarf Irregular Galaxies written by Irini Pantelaki and published by . This book was released on 1988 with total page 143 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Formation and Evolution of Galaxy Disks written by José G. Funes and published by . This book was released on 2008 with total page 548 pages. Available in PDF, EPUB and Kindle. Book excerpt: "These are the proceedings of the international conference "Formation and Evolution of Galaxy Disks" organized by the Specola Vaticana (the Vatican Observatory). The meeting hosted 198 participants from 26 countries. The program consisted of 61 talks and about 130 poster papers. In 2000 the Vatican Observatory organized a conference on Galaxy Disks and Disk Galaxies, the proceedings of which were published in ASP Conference Series Vol. 230. Since that time, a great amount of work has been done in this very active field. October 2007 was deemed an appropriate time to hold another similar conference where outstanding senior and junior astronomers in this field could air new results. The conference was focused on the formation and evolution of galaxy disks and covered the following topics: (1) properties of nearby galaxy disks; (2) interstellar medium, star formation, and chemical evolution; (3) disk edges, outskirts, and environment; (4) accretion onto disks, interactions, and mergers; (5) secular evolution of disks and bar/spiral driven evolution of galaxies; (6) evolution of disk structural properties; and (7) disk formation in a hierarchical universe. This books is of interest for researchers in extragalactic astronomy. It presents an overview of the relevant results and the progress made in the field in the last seven years."--Publisher's website
