A Study of Warm Absorbers in Active Galactic Nuclei
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Release | : 2006 |
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Author | : Dev Raj Sadaula |
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Total Pages | : 0 |
Release | : 2022 |
Genre | : Active galactic nuclei |
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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.
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Total Pages | : 412 |
Release | : 2004 |
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Author | : Kian Luke O'Kelly Momtahan |
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Total Pages | : 0 |
Release | : 2013 |
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Author | : Kian Momtahan |
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Release | : 2013 |
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Author | : Stefanie Komossa |
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Total Pages | : 18 |
Release | : 2000 |
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Author | : Robert Ross Gibson |
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Total Pages | : 184 |
Release | : 2006 |
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(Cont.) Either multiple factors influence line strength on observable time scales, or the line of sight to the central source varies over time through a structured absorber. In the third study, we survey spectra from the HETG data archive. We model the normalized excess variance (NEV) spectrum of a varying WA and find that it does not explain high-energy (> 2 keV) spectral variation, nor does it generally fit NEV spectra at lower energies (
Author | : Hagai Netzer |
Publisher | : Cambridge University Press |
Total Pages | : 369 |
Release | : 2013-09-16 |
Genre | : Science |
ISBN | : 1107021510 |
A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.
Author | : Volker Beckmann |
Publisher | : John Wiley & Sons |
Total Pages | : 390 |
Release | : 2012-09-24 |
Genre | : Science |
ISBN | : 3527410783 |
Active Galactic Nuclei This AGN textbook gives an overview on the current knowledge of the Active Galacitc Nuclei phenomenon. The spectral energy distribution will be discussed, pointing out what can be observed in different wavebands. The different physical models are presented together with formula important for the understanding of AGN physics. Furthermore, the authors discuss the AGN with respect to its environment, host galaxy, feedback in galaxies and in clusters of galaxies, variability, etc. and finally the cosmological evolution of the AGN phenomenon. This book includes phenomena based on new results in the X-Ray and gamma-ray domain from new telescopes such as Chandra, XMM-Newton, the Fermi Gamma-Ray Space Telescope, and the VHE regime not mentioned so far in AGN books. Those and other new developments as well as simulations of AGN merging events and formations, enabled through latest super-computing capabilities. From the contents: The observational picture of AGN Radiative processes The central engine AGN types and unification AGN through the electromagnetic spectrum AGN variability Environment Quasars and cosmology Formation, evolution and the ultimate fate of AGN What we do not know (yet)
Author | : James Howard Wurster |
Publisher | : |
Total Pages | : 440 |
Release | : 2013 |
Genre | : Active galactic nuclei |
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