[PDF] Gas Accretion Onto Galaxies eBook

Author : Andrew Fox
Publisher : Springer
Page : 386 pages
File Size : 14,88 MB
Release : 2017-03-23
Category : Science
ISBN : 3319525123

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This edited volume presents the current state of gas accretion studies from both observational and theoretical perspectives, and charts our progress towards answering the fundamental yet elusive question of how galaxies get their gas. Understanding how galaxies form and evolve has been a central focus in astronomy for over a century. These studies have accelerated in the new millennium, driven by two key advances: the establishment of a firm concordance cosmological model that provides the backbone on which galaxies form and grow, and the recognition that galaxies grow not in isolation but within a “cosmic ecosystem” that includes the vast reservoir of gas filling intergalactic space. This latter aspect in which galaxies continually exchange matter with the intergalactic medium via inflows and outflows has been dubbed the “baryon cycle”. The topic of this book is directly related to the baryon cycle, in particular its least well constrained aspect, namely gas accretion. Accretion is a rare area of astrophysics in which the basic theoretical predictions are established, but the observations have been as yet unable to verify the expectations. Accretion has long been seen around the Milky Way in so-called High Velocity Clouds, but detecting accretion even around nearby galaxies has proved challenging; its multi-phase nature requires sensitive observations across the electromagnetic spectrum for full characterization. A promising approach involves looking for kinematic signatures, but accretion signatures are often confused with internal motions within galaxies. Accretion studies therefore touch a wide range of astrophysical processes, and hence a wide cross-section of the astronomical community. As observational facilities are finally able to access the wavelength ranges and depths at which accretion processes may be manifest, the time is right to survey these multiple lines of investigation and determine the state of the field in accretion studies of the baryon cycle.

Author : Muhammad Latif
Publisher : World Scientific
Page : 376 pages
File Size : 33,53 MB
Release : 2019-04-26
Category : Science
ISBN : 9813227966

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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.

Author : Yujin Yang
Publisher :
Page : 476 pages
File Size : 17,35 MB
Release : 2008
Category :
ISBN :

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This thesis focuses primarily on how two important processes --- galaxymergers and gas accretion from the surrounding intergalactic medium ---affect the evolution of galaxies. Using post-starburst, or E+A, galaxies as a marker sample that undergoesa rapid transition from gas-rich star-forming galaxies to quiescent, passively-evolving E/S0s, we study what triggers E+A evolution andwhat E+A galaxies will become after the fading of their young stellarpopulation. With high resolution HST WFPC2/ACS imaging, we investigatetheir small and large scale properties, including their detailedmorphologies, bulge fractions, color gradients, scaling relationships, and newly formed star-clusters. 70% of E+A galaxies show disturbancesand tidal features indicating a merger origin and all their propertiesare either consistent with those of E/S0s or, if left to evolve passively, will become like those of early-types. Using cosmological simulations, we study hydrogen and helium gravitationalcooling radiation from gas accretion by young galaxies, finding thatobserving optically thin cooling lines such as HeII 1640 and hydrogenHalpha is critical in understanding the nature of galaxies forming viagas-accretion. To obtain an unbiased sample of Lyman alpha blobs thatwill allow us to follow-up their optically thin Halpha lines in the NIR, we conduct a blind, wide-field, narrow-band imaging survey for Lymanalpha blobs. After searching over 4.82 deg2̂, we discover four blobsthat we spectroscopically confirm to lie at z=2.3. The properties ofthese blobs are diverse: two blobs are X-ray-detected and have broadoptical emission lines (e.g., CIV) characteristic of AGN. The other50\% of blobs are not X-ray or optically-detected as AGN down tosimilar limits. The number density of the four blobs is extremely low,3̃ x 10-̂6 Mpc-̂3, comparable to that of galaxy clusters at similarredshifts. The two X-ray undetected blobs are separated by only70"(550 kpc) and have almost identical redshifts (corresponding to

Author : Juhan Frank
Publisher : Cambridge University Press
Page : 390 pages
File Size : 40,23 MB
Release : 2002-01-17
Category : Science
ISBN : 9780521629577

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Accretion Power in Astrophysics examines accretion as a source of energy in both binary star systems containing compact objects, and in active galactic nuclei. Assuming a basic knowledge of physics, the authors describe the physical processes at work in accretion discs and other accretion flows. The first three chapters explain why accretion is a source of energy, and then present the gas dynamics and plasma concepts necessary for astrophysical applications. The next three chapters then develop accretion in stellar systems, including accretion onto compact objects. Further chapters give extensive treatment of accretion in active galactic nuclei, and describe thick accretion discs. A new chapter discusses recently discovered accretion flow solutions. The third edition is greatly expanded and thoroughly updated. New material includes a detailed treatment of disc instabilities, irradiated discs, disc warping, and general accretion flows. The treatment is suitable for advanced undergraduates, graduate students and researchers.

Author : I. Pérez-Fournon
Publisher : Cambridge University Press
Page : 302 pages
File Size : 21,23 MB
Release : 2003-03-20
Category : Science
ISBN : 9780521825917

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This volume presents lectures of the XI Canary Islands Winter School of Astrophysics written by experts in the field.

Author : Dylan Nelson
Publisher :
Page : pages
File Size : 10,79 MB
Release : 2015
Category :
ISBN :

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Despite significant advances in the numerical modeling of galaxy formation and evolution, it is clear that a satisfactory theoretical picture of how galaxies acquire their baryons across cosmic time remains elusive. In this thesis we present a computational study which seeks to address the question of how galaxies get their gas. We make use of new, more robust simulation techniques and describe the first investigations of cosmological gas accretion using a moving-mesh approach for solving the equations of continuum hydrodynamics.

Author : National Research Council
Publisher : National Academies Press
Page : 401 pages
File Size : 31,96 MB
Release : 2002-02-07
Category : Science
ISBN : 0309070376

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In preparing the report, Astronomy and Astrophysics in the New Millenium , the AASC made use of a series of panel reports that address various aspects of ground- and space-based astronomy and astrophysics. These reports provide in-depth technical detail. Astronomy and Astrophysics in the New Millenium: An Overview summarizes the science goals and recommended initiatives in a short, richly illustrated, non-technical booklet.

Author : Ignacio Ferreras
Publisher : UCL Press
Page : 200 pages
File Size : 41,72 MB
Release : 2019-04-02
Category : Science
ISBN : 1911307614

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Galaxies, along with their underlying dark matter halos, constitute the building blocks of structure in the Universe. Of all fundamental forces, gravity is the dominant one that drives the evolution of structures from small density seeds at early times to the galaxies we see today. The interactions among myriads of stars, or dark matter particles, in a gravitating structure produce a system with fascinating connotations to thermodynamics, with some analogies and some fundamental differences. Ignacio Ferreras presents a concise introduction to extragalactic astrophysics, with emphasis on stellar dynamics, and the growth of density fluctuations in an expanding Universe. Additional chapters are devoted to smaller systems (stellar clusters) and larger ones (galaxy clusters). Fundamentals of Galaxy Dynamics, Formation and Evolution is written for advanced undergraduates and beginning postgraduate students, providing a useful tool to get up to speed in a starting research career. Some of the derivations for the most important results are presented in detail to enable students appreciate the beauty of maths as a tool to understand the workings of galaxies. Each chapter includes a set of problems to help the student advance with the material.