Download or read book Multi wavelength Observations of High Accretion Rate Type 1 Active Galactic Nuclei and Other Super Soft X ray Sources written by Mark Simpson and published by . This book was released on 2010 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The study of X-ray emission from AGN allows the investigation of the inner regions of their central engine. By understanding the processes taking place within AGN, many other areas of research will benefit, such as accretion and the formation and evolution of galaxies. This thesis begins by investigating the background AGN population of the serendipitous sources detected in a deep-look (~ 500 ks) of the XMM-Newton field of view surrounding 3C 273. The deep-look is created by mosaicing XMM-Newton EPIC calibration observations of 3C 273. Time averaged spectra of the 17 brightest X-ray sources are analysed. Cross-correlation of the X-ray sources with catalogues at other wavelengths is performed and unique candidate counterparts proposed. Classification of the X-ray sources is attempted and the background AGN population is discussed. A number of AGN have shown evidence of high-ionisation, high-velocity outflows in their X-ray spectra. These sources are believed to have a high-accretion rate at or near the Eddington limit. Six suspected high-accretion rate narrow line AGN observed with XMM-Newton are analysed and inspected for the presence of these outflows. No such outflows are detected. However, three of the targets did show evidence of mass loss in the form of a warm absorber. In addition, all of the sources appear to have a soft excess below ~2 keV. Finally, a search for the AGN population of super soft X-ray sources (SSXs) in the first and second XMM-Newton catalogues is performed. Hardness ratios are used to search for SSXs, which are defined as having a characteristic temperature, kT>~100 eV. Cross-correlation of the selected SSXs with catalogues at other wavelengths is performed, returning both Galactic and extragalactic candidate counterparts. For a small number of SSXs with previously unclassified optical candidate counterparts, optical spectroscopic observations were acquired. The analysis of these observations identified 5 previously unclassified AGN.

Download or read book Active Galactic Nuclei Studies in Cosmic X ray Survey Fields written by Qingling Ni and published by . This book was released on 2021 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: X-ray surveys are an effective way to study growing supermassive black holes (SMBHs) in galaxy centers, as actively accreting SMBHs manifest themselves as active galactic nuclei (AGN) that can be observed in the X-ray in most cases. Through studying AGNs in X-ray survey fields that have extensive multiwavelength data coverage, we can probe how SMBH growth links with their host galaxies over cosmic history. Previously, researchers mainly linked SMBH growth with stellar mass (M⋆) or star formation rate (SFR). In this dissertation, we utilize morphological information to show that among star-forming (SF) galaxies, long-term average SMBH accretion rate (BHAR) relates to host-galaxy compactness (Chapter 2). We found that the relation between BHAR and host-galaxy compactness is more fundamental than the relation between BHAR and M⋆ or SFR (Chapter 3). This dissertation also provides key results from the XMM-Spitzer Extragalactic Representative Volume Survey (XMM-SERVS), which will benefit studies of SMBH growth in the next decade with a large sample of AGNs that have superb multiwavelength data. The detection of X-ray point sources in two of the XMM-SERVS survey fields is presented in Chapter 4. In Chapter 5, multiwavelength counterpart identification, photometric-redshift calculation, and source classification for X-ray sources in the XMM-SERVS survey fields are presented; most of the X-ray point-like sources detected are classified as AGNs, showing SMBH growth over the full range of cosmic environments. A Hyper Suprime-Cam (HSC) forced-photometry catalog that provides optical coverage for one of the XMM-SERVS survey fields is presented in Chapter 6. Apart from these works that focus on "Active Galactic Nuclei Studies in Cosmic X-ray Survey Fields", this dissertation also includes my other two first-author works in the appendices, where X-ray observational studies of weak-line quasars (WLQs) are presented. By studying these quasars with exceptional spectroscopic properties, we found good supporting evidence for optically thick inner accretion disks among quasars with high Eddington ratios.

Download or read book Probing the Physics of Active Galactic Nuclei by Multiwavelength Monitoring written by Bradley M. Peterson and published by . This book was released on 2001 with total page 568 pages. Available in PDF, EPUB and Kindle. Book excerpt: Annotation Papers from a June 2000 meeting discuss multiwavelength monitoring methods for studying active galactic nuclei, the potential of dedicated facilities for multiwavelength monitoring, and future multiwavelength programs. Some topics discussed are multiwavelength observations of blazars, time delays of blazar flares observed at different wavebands, low radiative-efficiency accretion flows, spectrochronography, and variability of the intrinsic UV absorption lines in Seyfert galaxies. Other topics are the variable diffuse continuum emission of broad-line clouds, the MIDEX concept, and the mission. Peterson teaches astronomy at The Ohio State University. This volume lacks a subject index. Annotation c. Book News, Inc., Portland, OR (booknews.com)

Download or read book Multiwavelength Observations of Active Galactic Nuclei from the Radio to the Hard X rays written by Tobias Beuchert and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book The X ray Background written by Xavier Barcons and published by Cambridge University Press. This book was released on 1992-07-31 with total page 328 pages. Available in PDF, EPUB and Kindle. Book excerpt: A review of the current observational knowledge and understanding of the cosmic X-ray background.

Download or read book The Physics and Evolution of Active Galactic Nuclei written by Hagai Netzer and published by Cambridge University Press. This book was released on 2013-09-16 with total page 369 pages. Available in PDF, EPUB and Kindle. Book excerpt: A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.

Download or read book High Energy Studies of Active Galactic Nuclei with XMM Newton written by Rebecca Jane Smith and published by . This book was released on 2009 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Multi wavelength Observations of Active Galactic Nuclei written by Thierry Jean-Louis Courvoisier and published by . This book was released on 1994 with total page 5 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Multi wavelength Studies of Active Galactic Nuclei on Parsec and Kiloparsec Scales written by Juan Carlos Algaba and published by . This book was released on 2010 with total page 177 pages. Available in PDF, EPUB and Kindle. Book excerpt: Although the continua of radio-loud Active Galactic Nuclei (AGN) are typically dominated by synchrotron radiation over virtually the entire spectrum, it is not clear whether the radio and higher-frequency emission originate in the same or different parts of the jet. In some inhomogeneous synchrotron source models for blazars, the radio and UV-optical-IR (UVOIR) emission may be co-spatial, depending on the model parameters considered. Indeed, several different radio{u2013}optical correlations based on polarization data have been found recently, suggesting that the optical and radio polarization may be closely related, and that the corresponding emission regions may be cospatial. My joint analysis of optical and 15+22+43 GHz VLBA polarization data for a sample of about 40 AGNs shows that, after correction for the inferred VLBA core Faraday rotations, most BL Lac objects and some quasars have aligned VLBA-core and optical polarizations, although many quasars also show no obvious relationship between their VLBA-core and optical polarization angles. This apparently indicates that not all AGNs have co-spatial regions of optical and radio emission in their jets. However, another possibility was that some of the 15{u2013}43 GHz VLBA cores have Faraday rotations of the order of several tens of thousand of rad/m2, which were not properly fit using our three-frequency data due to n {u00D7} _ ambiguities in the observed polarization angles, leading to incorrect subtraction of the effects of the core Faraday rotation, and so incorrect {u2018}zero-wavelength{u2019} radio polarization angles. With this is mind, I obtained additional observations for 8 of the 40 AGN, this time at 12+15+22+24+43 GHz, chosen in such a way that we should be able to discern between various possible scenarios. My results indicate that, although some VLBI radio cores have comparatively high rotation measures, this cannot explain the misalignments found between the radio core and optical VLBI polarization angles. I performed a series of analyse to check if this could be explained by other physical processes or properties occurring in the AGN, such as degree of polarization, magnetic field intensity or presence of detectable {u2013}ray emission. No clear differences between the properties of sources with aligned and misaligned radio-core and optical polarization angles was found. The emission from AGN is mostly synchrotron in origin, making it natural that the degree of circular polarization (CP) is low, less than a percent. For this reason, the detection of CP is a non trivial task. However, using recently developed new techniques, I have performed circular polarization analysis on some of my sources. The results indicate that the degree of CP tends to increase with frequency, with the spectral index being either flat or inverted, _ _ +1, which can be explained with a Blandford-Königl jet model. Using the measured intensity, spectral indices and magnetic fields derived from the measured core shift, I have derived the degree of order of the magnetic field required to explain if this observed CP is generated by the synchrotron mechanism. The implied degrees of order of the magnetic field are too high in most cases for the CP to be synchrotron in origin, requiring a substantial (possible dominant) contribution from Faraday conversion of linear to circular polarizaton. A kilo-Parsec multiwavelength study has also been performed on the source PKS 0521{u2013}365. This AGN has been classified as a HYMOR (Hybrid morphology radio source) and has a jet which is clearly detectable over a wide frequency band, ranging from radio to X-rays. This has allowed me to perform a study of its physical properties over radio, near infra-red, optical and X-rays bands, thus obtaining valuable information about its morphology, spectral energy distribution and magnetic field. The data here supports the hypothesis that PKS0521-36 is intermediate between an FRI and FRII source, agreeing with unified scenarios in which the differences between these classes can be understood on a physical basis.

Download or read book A Study of the X ray and Optical Variability of the Active Galactic Nucleus ESO 362 G18 written by Beatriz Agís González and published by . This book was released on 2017 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: The standard UnifiedModel (UM) of Active Galactic Nuclei, established 30 years ago, has been key to shed light in the taxonomy of such a heterogenous class of objects. Its basic premise is the ubiquitous presence of an obscuring torus around the central engine, so that the observed diversity simply reflects different viewing angles of an axisymmetric geometry. Consequently, type 1 AGNs are observed with a direct view of fast moving material close to the super massive black hole (SMBH), resulting in broad emission lines in their optical/UV spectra, while type-2 AGNs are observed from a more edge-on view, intercepting the obscuring torus that blocks the broad emission line region (BLR) component from our line of sight (LOS). This scheme was consolidated with the discovery of polarized broad emission lines (PBLs), also known as hidden broad-line regions (HBLRs), in the type 2 AGN, hence presenting the same properties as type 1 nuclei in polarized light. Nowadays, additional ingredients are likely needed to account for some observational facts that are apparently in conflict with the predictions. For instance, the UM predicts the absorbing torus as an homogeneous and uniform structure. There is broad evidence, especially at infrared wavelengths, that the dusty torus is indeed clumpy instead uniform. The general goal of this thesis is to endorse the current evidence for the clumplyness of the key element of the standard UM from other wavelengths: X-rays, UV and optical. To this end, we will focus on the study of the absorption variability performed by an interesting Seyfert galaxy: ESO 362-G18. This source gets our whole attention because it is usually classified as a type 1 AGN, however a spectrum retrieved from the 6 degree Galaxy Survey (6dFGS) shows the optical spectrum of ESO 362-G18 to lack its broad emission lines. This type 2 spectrum suggests ESO 362-G18 to be a changing look Seyfert galaxy. This rare type of sources represents a violation of the UMand probes that its corresponding classification is not only angle-dependent. Thus, we decided to start a deep multi-wavelength analysis of ESO 362-G18 to get as many complementary views as possible and approach the intriguing nature of this source...

Download or read book Quasars at All Cosmic Epochs written by Paola Marziani and published by Frontiers Media SA. This book was released on 2018-10-05 with total page 447 pages. Available in PDF, EPUB and Kindle. Book excerpt: The last 50 years have seen a tremendous progress in the research on quasars. From a time when quasars were unforeseen oddities, we have come to a view that considers quasars as active galactic nuclei, with nuclear activity a coming-of-age experienced by most or all galaxies in their evolution. We have passed from a few tens of known quasars of the early 1970s to the 500,000 listed in the catalogue of the Data Release 14 of the Sloan Digital Sky Survey. Not surprisingly, accretion processes on the central black holes in the nuclei of galaxies — the key concept in our understanding of quasars and active nuclei in general — have gained an outstanding status in present-day astrophysics. Accretion produces a rich spectrum of phenomena in all bands of the electromagnetic spectrum. The power output of highly-accreting quasars has impressive effects on their host galaxies. All the improvement in telescope light gathering and in computing power notwithstanding, we still miss a clear connection between observational properties and theory for quasars, as provided, for example, by the H-R diagram for stars. We do not yet have a complete self-consistent view of nuclear activity with predictive power, as we do for main-sequence stellar sources. At the same time quasars offer many “windows open onto the unknown". On small scales, quasar properties depend on phenomena very close to the black hole event horizon. On large scales, quasars may effect evolution of host galaxies and their circum-galactic environments. Quasars’ potential to map the matter density of the Universe and help reconstruct the Universe’s spacetime geometry is still largely unexploited. The times are ripe for a critical assessment of our present knowledge of quasars as accreting black holes and of their evolution across the cosmic time. The foremost aim of this research topic is to review and contextualize the main observational scenarios following an empirical approach, to present and discuss the accretion scenario, and then to analyze how a closer connection between theory and observation can be achieved, identifying those aspects of our understanding that are still on a shaky terrain and are therefore uncertain knowledge. This research topic covers topics ranging from the nearest environment of the black hole, to the environment of the host galaxies of active nuclei, and to the quasars as markers of the large scale structure and of the geometry of spacetime of the Universe. The spatial domains encompass the accretion disk, the emission and absorption regions, circum-nuclear starbursts, the host galaxy and its interaction with other galaxies. Systematic attention is devoted to some key problems that remain outstanding and are clearly not yet solved: the existence of two quasar classes, radio quiet and radio loud, and in general, the systematic contextualization of quasar properties the properties of the central black hole, the dynamics of the accretion flow in the inner parsecs and the origin of the accretion matter, the quasars’ small and large scale environment, the feedback processes produced by the black hole into the host galaxy, quasar evolutionary patterns from seed black holes to the present-day Universe, and the use of quasars as cosmological standard candles. The timing is appropriate as we are now witnessing a growing body of results from major surveys in the optical, UV X, near and far IR, and radio spectral domains. Radio instrumentation has been upgraded to linear detector — a change that resembles the introduction of CCDs for optical astronomy — making it possible to study radio-quiet quasars at radio frequencies. Herschel and ALMA are especially suited to study the circum-nuclear star formation processes. The new generation of 3D magnetohydrodynamical models offers the prospective of a full physical modeling of the whole quasar emitting regions. At the same time, on the forefront of optical astronomy, applications of adaptive optics to long-slit spectroscopy is yielding unprecedented results on high redshift quasars. Other measurement techniques like 2D and photometric reverberation mapping are also yielding an unprecedented amount of data thanks to dedicated experiments and instruments. Thanks to the instrumental advances, ever growing computing power as well as the coming of age of statistical and analysis techniques, the smallest spatial scales are being probed at unprecedented resolution for wide samples of quasars. On large scales, feedback processes are going out of the realm of single-object studies and are entering into the domain of issues involving efficiency and prevalence over a broad range of cosmic epochs. The Research Topic "Quasars at all Cosmic Epochs" collects a large fraction of the contributions presented at a meeting held in Padova, sponsored jointly by the National Institute for Astrophysics, the Padova Astronomical Observatory, the Department of Physics and Astronomy of the University of Padova, and the Instito de Astrofísica de Andalucía (IAA) of the Consejo Superiór de Investigación Cientifica (CSIC). The meeting has been part of the events meant to celebrate the 250th anniversary of the foundation of the Padova Observatory.

Download or read book International Aerospace Abstracts written by and published by . This book was released on 1999 with total page 974 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Robotic Observatories written by M. F. Bode and published by John Wiley & Sons. This book was released on 1995 with total page 176 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book An Introduction to Active Galactic Nuclei written by Bradley M. Peterson and published by Cambridge University Press. This book was released on 1997-02-13 with total page 258 pages. Available in PDF, EPUB and Kindle. Book excerpt: 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.

Download or read book Multi Wavelength Continuum Emission of AGN written by T.J.-L. Courvoisier and published by Springer. This book was released on 1994-05-14 with total page 0 pages. Available in PDF, EPUB and Kindle. Book excerpt: Active Galactic Nuclei radiate over the electro-magnetic spectrum from radio waves to gamma rays. Understanding the physics of these objects therefore requires the synthesis of results from many different domains of Astronomy. It was the aim of the conference "Active Galactic Nuclei across the Electromagnetic Spectrum" to provide a forum where this exchange could take place. Some 300 astronomers participated to the conference, 250 of them presented results either as oral papers or in the form of posters. Observations in all domains of the electro magnetic spectrum in which astronomical observations can be made from the ground or from space were presented. Many theoretical contributions were also given. There has been a tremendous growth in the number and quality of Astronomical obser vations in many spectral domains over the past several years. Students of Active Galactic Nuclei have been particularly keen to make use of the available facilities (both space born and on the ground), often in a very organised way, in order to obtain repeated simultane ous data covering large bands of the spectrum. This approach has produced a qualitatively new set of data for understanding the physics of Active Galactic Nuclei. The task of the meeting was to review this data in a coherent way.

Download or read book Active Galactic Nuclei written by Professor R. D. Blandford and published by Springer. This book was released on 2013-12-14 with total page 289 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Literature 1992 Part 1 written by Astronomisches Recheninstitut and published by Springer Science & Business Media. This book was released on 2013-11-11 with total page 1456 pages. Available in PDF, EPUB and Kindle. Book excerpt: "Astronomy and Astrophysics Abstracts" appearing twice a year has become oneof the fundamental publications in the fields of astronomy, astrophysics andneighbouring sciences. It is the most important English-language abstracting journal in the mentioned branches. The abstracts are classified under more than a hundred subject categories, thus permitting a quick survey of the whole extended material. The AAA is a valuable and important publication for all students and scientists working in the fields of astronomy and related sciences. As such it represents a necessary ingredient of any astronomical library all over the world.