Photoionization Modelling as a Density Diagnostic of Line Emitting/Absorbing Regions in Active Galactic Nuclei

Photoionization Modelling as a Density Diagnostic of Line Emitting/Absorbing Regions in Active Galactic Nuclei
Author: Tek Prasad Adhikari
Publisher: Springer
Total Pages: 126
Release: 2019-06-29
Genre: Science
ISBN: 3030227375

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This book presents timely work on the nature of the physical processes underpinning two of the basic characteristics of the gas structure in the innermost region of Active Galactic Nuclei (AGN): ionized outflows and emission line regions. In addition, it describes physics-based methods for estimating the density of the astrophysical plasma surrounding AGN. All numerical computations of the photoionized gas employ the most advanced codes available (CLOUDY and TITAN). Calculations of the radiative transfer are based on the assumption of thermal and ionization equilibrium. Promising preliminary examples of comparison with current observations are included for several individual AGN. All of them suggest that the absorbing/emitting gas should have a density on the order of 1012 cm-3. Future observations will provide more objects to verify these results, and will allow us to put constraints on the launch radius of ionized outflows and therefore on the mass loading and kinetic energy outflow rates. These rates, in turn, are crucial to estimating whether the outflows have a significant feedback impact on star formation and metal enrichment in the interstellar medium of the host galaxy. In closing, the book discusses a representative example of applying powerful photoionization techniques to explain the complex physics of the AGN environment.

Active Galactic Nuclei

Active Galactic Nuclei
Author: Professor R. D. Blandford
Publisher: Springer
Total Pages: 289
Release: 2013-12-14
Genre: Science
ISBN: 3662398168

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Central Activity in Galaxies

Central Activity in Galaxies
Author: Aage Sandqvist
Publisher: Springer
Total Pages: 264
Release: 1993-01-22
Genre: Science
ISBN:

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This outstanding collection of surveys addresses graduate and predoctoral students. It reports on theoretical research and observational data on active galactic nuclei: The enigma of the nuclei of galaxies with their central "monster" driving the vast range of activity observed in quasars, radio galaxies, Seyferts, starburst galaxies and even our own Galaxy are explored in this volume. Topics covered include: the impact of recent measurements in the infrared and radio region on our knowledge of thenucleus of our Galaxy; the spectra and classification of active galactic nuclei, the properties of their host galaxies, their cosmological distribution and evolution, the role of stars and thehydrodynamics of the interstellar medium in the nuclei; the description of the inner parsec of a standard active galactic nucleus based on direct interpretation of the observations; the infrared activity of galaxies; the physics of radio galaxies and their jets, emphasizing the physics ofgas flow and high-energy particle interactions as well as shock acceleration. These are all discussed in considerable depth and presented inself-contained chapters with exhaustive reference lists of the scientific literature.

Astrophysics Of Gas Nebulae and Active Galactic Nuclei

Astrophysics Of Gas Nebulae and Active Galactic Nuclei
Author: Donald E. Osterbrock
Publisher: University Science Books
Total Pages: 488
Release: 2006
Genre: Science
ISBN: 9781891389344

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Thoroughly revised and expanded throughout, the new edition is a graduate-level text and reference book on gaseous nebulae, nova and supernova remnants. Much of the new data and new images are from the Hubble Space Telescope with two wholly new chapters being added along with other new features. The previous edition which was tried and tested for thirty years has now been succeeded by a revised, updated, larger edition, which will be valuable to anyone seriously interested in astrophysics.

Time-dependent Photoionization Modeling of Warm Absorbers in Active Galactic Nuclei

Time-dependent Photoionization Modeling of Warm Absorbers in Active Galactic Nuclei
Author: Dev Raj Sadaula
Publisher:
Total Pages: 0
Release: 2022
Genre: Active galactic nuclei
ISBN:

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Warm absorber spectra are bound-bound and bound-free absorption features, seen in the X-ray and UV spectra from many active galactic nuclei (AGN). The widths and centroid energies of these features indicate they occur in outflowing gas moving with hundreds to thousands of km/s. Depending upon the energy and momentum of the outflow, it can affect the gas within the host galaxy. Thus, warm absorbers’ mass and energy budgets are of great interest. Estimates for these properties depend on models that connect the absorption features' observed strengths with the density, composition, and ionization state of the absorbing gas. Such models assume that the ionization and heating of the gas are determined primarily by the strong continuum radiation from near the central black hole. They also assume that the various heating, cooling, ionization, and recombination processes are in a time-steady balance. However, this assumption may not be valid, owing to the intrinsic time-variability of the illuminating continuum or other factors like sudden adiabatic expansion and gas moving with high speed, which changes the cloud environment. Understanding outflowing gas, including warm absorbers, is crucial for understanding the AGN. We study the properties of such outflow exposed to the highly variable ionizing source using time-dependent calculations, which is different from equilibrium modeling commonly approached in modeling the photoionized gas. To model the outflow, we numerically solved the time-dependent forms of the balance equations for ionization, internal energy, and radiative transfer in a self-consistent manner. A new computer code is deployed to investigate the properties and associated spectrum for various warm absorber models. This study presents models for warm absorbers which follow the time dependence of the ionization, temperature, and radiation field in gas clouds in response to a changing continuum illumination. We show that the effects of time variability are essential over a range of parameters and that time-dependent models differ from equilibrium models in meaningful ways. Thus time-dependent effects should be included in models that derive properties of warm absorber outflows.

An Introduction to Active Galactic Nuclei

An Introduction to Active Galactic Nuclei
Author: Bradley M. Peterson
Publisher: Cambridge University Press
Total Pages: 258
Release: 1997-02-13
Genre: Science
ISBN: 9780521479110

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How can we test if a supermassive black hole lies at the heart of every active galactic nucleus? What are LINERS, BL Lacs, N galaxies, broad-line radio galaxies and radio-quiet quasars and how do they compare? This timely textbook answers these questions in a clear, comprehensive and self-contained introduction to active galactic nuclei - for graduate students in astronomy and physics. The study of AGN is one of the most dynamic areas of contemporary astronomy, involving one fifth of all research astronomers. This textbook provides a systematic review of the observed properties of AGN across the entire electromagnetic spectrum, examines the underlying physics, and shows how the brightest AGN, quasars, can be used to probe the farthest reaches of the Universe. This book serves as both an entry point to the research literature and as a valuable reference for researchers in the field.

Astrophysics of the Diffuse Universe

Astrophysics of the Diffuse Universe
Author: Michael A. Dopita
Publisher: Springer Science & Business Media
Total Pages: 445
Release: 2013-06-29
Genre: Science
ISBN: 3662058669

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The reference work on astrophysics to provide a comprehensive introduction to the physics of Interstellar Matter. The objective of the book is to show how physics can be applied to the understanding and diagnosis of the phase structure, the physical conditions and the chemical make-up and evolution of the interstellar medium. Unlike other textbooks in the field, here a more systematic approach has been adopted based on the authors' lecture course experience. It is aimed primarily at those undertaking post-graduate courses, or those doing advanced projects as part of honours undergraduate courses in physics or astrophysics.

The Physics and Evolution of Active Galactic Nuclei

The Physics and Evolution of Active Galactic Nuclei
Author: Hagai Netzer
Publisher: Cambridge University Press
Total Pages: 369
Release: 2013-09-16
Genre: Science
ISBN: 1107021510

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A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.