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Author: Hirofumi Noda Publisher: Springer ISBN: 9812877215 Category : Science Languages : en Pages : 164
Book Description
The aim of this research was to use the X-ray satellite Suzaku to establish a picture of a central engine that effectively converts the gravitational energy of accreting matter onto the supermassive black hole to a huge amount of radiation in an active galactic nucleus. Although the engine is known to consist of a Comptonizing corona and an accretion disk, its image has remained unclear because primary emissions, coming directly from the engine, cannot be identified in X-ray spectra without models. The book describes a technique of time variability assisted spectral decomposition to model-independently examine X-ray signals, and how this was applied to the Suzaku archive data of active galactic nuclei. As a result, at least three distinct primary X-ray components have been discovered in an X-ray from an active galactic nucleus, presumably indicating a novel picture that the engine is composed of multiple coronae with different physical properties in an accretion flow. Furthermore, the determination of the spectral shapes of the primary X-rays has a significant impact on estimations of black hole spins, because it is essential to quantify reprocessed X-ray spectra. The successful model-independent decomposition of X-ray spectral components with flux variations of active galactic nuclei is likely to be effective in future data analyses from the soon-to-be-launched Japanese X-ray satellite ASTRO-H, which is capable of achieving unprecedented fine spectros copy and broad energy band coverage.
Author: Hirofumi Noda Publisher: Springer ISBN: 9812877215 Category : Science Languages : en Pages : 164
Book Description
The aim of this research was to use the X-ray satellite Suzaku to establish a picture of a central engine that effectively converts the gravitational energy of accreting matter onto the supermassive black hole to a huge amount of radiation in an active galactic nucleus. Although the engine is known to consist of a Comptonizing corona and an accretion disk, its image has remained unclear because primary emissions, coming directly from the engine, cannot be identified in X-ray spectra without models. The book describes a technique of time variability assisted spectral decomposition to model-independently examine X-ray signals, and how this was applied to the Suzaku archive data of active galactic nuclei. As a result, at least three distinct primary X-ray components have been discovered in an X-ray from an active galactic nucleus, presumably indicating a novel picture that the engine is composed of multiple coronae with different physical properties in an accretion flow. Furthermore, the determination of the spectral shapes of the primary X-rays has a significant impact on estimations of black hole spins, because it is essential to quantify reprocessed X-ray spectra. The successful model-independent decomposition of X-ray spectral components with flux variations of active galactic nuclei is likely to be effective in future data analyses from the soon-to-be-launched Japanese X-ray satellite ASTRO-H, which is capable of achieving unprecedented fine spectros copy and broad energy band coverage.
Author: Francoise COMBES Publisher: Springer Science & Business Media ISBN: 9783540419273 Category : Science Languages : en Pages : 468
Book Description
Unique in its breadth of coverage and level of presentation, this revised textbook provides more on the nature of galaxies, extragalactic objects, the large-scale structure of the Universe, and cosmology than is available in general textbooks on astronomy. It remains, however, accessible to advanced undergraduate students. One or more chapters are devoted to each of the following: the classification and morphology of galaxies; the galactic interstellar medium; galactic kinematics; elliptical, spiral, and barred spiral galaxies; the interactions between galaxies; extragalactic radio sources, quasars and their line spectra, and other active galactic nuclei; the formation of galaxies; the Universe as a whole; and cosmology.
Author: Jianfeng Wu Publisher: ISBN: Category : Languages : en Pages :
Book Description
Active galactic nuclei (AGNs) are ideal laboratories for fundamental physics and cosmology. Our knowledge of AGNs has been greatly advanced during the past decades thanks to the unprecedentedly powerful X-ray missions (e.g., Chandra, XMM-Newton, and Swift) and modern large area surveys in the optical/UV band (e.g., the Sloan Digital Sky Survey; SDSS). Studies on the relation between multiwavelength properties of AGNs can reveal the physics of AGN accretion process. In this dissertation, I mainly study the relation between the AGN X-ray properties and their optical/UV spectral properties on emission lines, absorption lines and continuum. I also investigate the X-ray properties of AGNs with extreme radio properties in the early Universe. (1) We studied the X-ray properties of a class of radio-quiet SDSS quasars with weak broad emission lines (weak-line quasars; WLQs). Although the WLQ population shows diverse X-ray properties, they have an excess of X-ray weak sources. Besides having weak emission lines, the X-ray weak WLQs generally show other unusual UV emission-line properties similar to those of the remarkable X-ray weak quasar PHL 1811 (e.g., highly blueshifted C IV lines, weak semi-forbidden lines, and strong UV Fe emission). They are classified as "PHL 1811 analogs". The X-ray weak WLQs also show a harder X-ray spectrum, while the WLQ with normal X-ray brightness have similar X-ray spectral properties to those of typical quasars. We proposed an AGN geometry which can potentially unify the X-ray weak and X-ray normal WLQ populations via orientation effect. The infrared-to-UV spectral energy distributions (SEDs) of X-ray weak and X-ray normal WLQs have consistent SEDs with those for typical quasars, which disfavors the BL Lac-like scenario for the nature of these quasars (Chapters 2 and 3). (2) We have led the best X-ray study to date on quasars with intermediate-width absorption lines (mini-BALs). We found the X-ray brightness of mini-BAL quasars are more close to those of typical quasars than to BAL quasars (which are generally X-ray weak), showing they do not have substantial X-ray absorption. Strong correlations were found between the X-ray brightness and UV absorption parameters, e.g., the absorption strength and maximum outflow velocity. We further proposed new UV absorption parameters which better correlate with the X-ray properties than existing parameters do (Chapter 4). (3) We studied the relation between the optical/UV luminosity and X-ray luminosity (quantified by the alpha_ox parameter) for the most-luminous quasars over a wide range of redshifts. Our correlation analyses provide better constraints on the alpha_ox-UV luminosity correlation. We have also verified that the alpha_ox parameter does not significantly evolve with redshift. We provide the individual and composite mid-infrared-to-UV SEDs for the most-luminous quasars. (Chapter 5). (4) We presented the X-ray and multiwavelength properties of the highly radio-loud quasars (HRLQs) at z > 4. Our HRLQs show a significant enhancement of X-ray emission over those HRLQs at lower redshift with similar optical/UV and radio luminosities, suggesting that the jet-linked X-ray emission mechanism in the early universe may differ from that in the more evolved universe. The optical/UV emission-line strength of RLQs are correlated with radio loudness, but not with relative X-ray brightness. Our HRLQs generally follow the anti-correlation between radio loudness and X-ray power-law photon index. We also studied the broad-band SEDs of HRLQs. Some HRLQs have an excess of mid-infrared emission which may originate from the jet synchrotron emission. None of our z > 4 HRLQs is detected by the Fermi LAT two-year survey (Chapter 6).
Author: Julian H. Krolik Publisher: Princeton University Press ISBN: 0691227470 Category : Science Languages : en Pages : 632
Book Description
This is the first comprehensive treatment of active galactic nuclei--the cosmic powerhouses at the core of many distant galaxies. The term active galactic nuclei refers to quasars, radio galaxies, Seyfert galaxies, blazars, and related objects, all of which are believed to share a similar central engine--a supermassive black hole many times the mass of the Sun. Astrophysicists have studied these phenomena for the past several decades and have begun to develop a consensus about many of their properties and internal mechanisms. Julian Krolik, one of the world's leading authorities on the subject, sums up leading ideas from across the entire range of research, making this book an invaluable resource for astronomers, physicists interested in applications of the theory of gravitation, and graduate students. Krolik begins by addressing basic questions about active galactic nuclei: What are they? How can they be found? How do they evolve? He assesses the evidence for massive black holes and considers how they generate power by accretion. He discusses X-ray and g-ray emission, radio emission and jets, emission and absorption lines, anisotropic appearance, and the relationship between an active nucleus and its host galaxy. He explores the mysteries of what ignites, fuels, and extinguishes active galactic nuclei, and concludes with a general review of where the field now stands. The book is unique in paying careful attention to relevant physics as well as astronomy, reflecting in part the importance of general relativity to understanding active galactic nuclei. Clear, authoritative, and detailed, this is crucial reading for anyone interested in one of the most dynamic areas of astrophysics today.
Author: Hirofumi Noda
Author: Hirofumi Noda
Author: R. F. Mushotsky
Author: Wolfgang Brinkmann
Author: Richard Mushotzky
Author: Francoise COMBES
Author: Joachim Trumper
Author: Xavier Barcons
Author: John David Silverman
Author: Jianfeng Wu
Author: Julian H. Krolik