A High Energy Study Of Active Galactic Nuclei
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Study of the Variability of Active Galactic Nuclei at Very High Energy with H.E.S.S.
| Author | : Gabriel Emery |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2020 |
| Genre | : |
| ISBN | : |
Along with the improvement of our knowledge of the Universe, increasingly detailed, varied and precise data sets appeared necessary to solve the remaining unknowns. Experiments thus improved their sensitivities and resolutions but also combined their observations into large multi-messenger and multi-wavelength data sets. If a source is variable the available temporal information can also be used to constrain the possible processes taking place in this source. Blazars are active galactic nuclei displaying important variability with electromagnetic emissions covering a large fraction of the observed electromagnetic spectrum, emitted in a relativistic jet of particles. The H.E.S.S. experiment is an array of Cherenkov telescopes located in Namibia performing astronomical observations using very high energy photons. In this manuscript, reviews of blazar physics, very high energy astronomy and the H.E.S.S. experiment are followed by various worked performed to analyse and use variable data from blazars. Tools were developed in the H.E.S.S. analysis software aiming at improving the analysis of flaring events. Sets of data obtained during flaring events of two blazars (3C 279 and PKS 2022-077) were analysed and put into context with contemporaneous multi-wavelength observations. A new task aiming at characterising blazar flare in a semi-systematic way is also introduced. The manuscript then ends with the results of the exploration of the parameter space of a lepto-hadronic emission model applied to a flare of TXS 0506+056 coincident with the detection of an astrophysical neutrino with IceCube.
High Energy Astrophysical Neutrinos
| Author | : Debanjan Bose |
| Publisher | : Springer Nature |
| Total Pages | : 75 |
| Release | : 2021-12-07 |
| Genre | : Science |
| ISBN | : 3030912582 |
This book provides a pedagogical introduction to the likely sources of these neutrinos, their propagation and detection mechanisms. Detection of high energy neutrinos of extragalactic origin has led to an interdisciplinary field of research, involving astronomy, astrophysics and particle physics. An extensive review of various detectors and the observations is provided that consolidates the latest findings. Above a few tens of TeVs, neutrinos are conceived as more reliable messengers for astronomy than photons as these photons get absorbed in the background photon field. Determining the neutrino spectrum not only helps in exploring astrophysical objects like AGN, GRB, etc. but also allows us to study particle physics at unprecedented energies. This introductory book is intended to help advanced undergraduate and graduate students to get into the subject with ease, and it simultaneously caters to practicing theoretical or experimental physicists as a reference book.
Active Galactic Nuclei
| Author | : Julian H. Krolik |
| Publisher | : Princeton University Press |
| Total Pages | : 632 |
| Release | : 1999-01-10 |
| Genre | : Science |
| ISBN | : 9780691011516 |
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.
High-energy Emission from Active Galactic Nuclei
| Author | : Matteo Cerruti |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2012 |
| Genre | : |
| ISBN | : |
. In this thesis manuscript we tried to summarize the research work done during the last three years in the high-energy group of the LUTh laboratory, as well as in the H.E.S.S. collaboration. The project deals with the study of high-energy emission from active galactic nuclei (AGN), where, with high energy, we refer here to X and y-rays. The thesis covers in fact two différent aspects of the physics of AGN, firstly the study of the X-ray emission from Seyfert galaxies (radio-quiet AGN), and then of the y-ray emission from blazars (radio-loud AGN).We start then by providing a short introduction to the scientific context of AGN physics (by present- ing the unified AGN model), as well as of TeV astronomy. In the first part we first describe the problem of the soft-X-ray excess in Seyfert galaxies (Chapter 1), before entering in the details of the study of Suzaku observations of two particular objects (Mrk 509 and Mrk 841, Chapter 2), presenting the data analysis and their modelling. The second part starts with an introduction on the blazar physics (Chapter 3), before showing the results achieved by the H.E.S.S. telescope array on AGN (Chapter 4). A detailed study has been done on a particular blazar detected at TeV energies (1RXS J101015.9 - 311909), and is presented in Chapter 5. The following chapters are more theoretical, and discuss the modelling of the observed blazar emis- sion. In particular, in Chapter 6 we discuss the constrains on the synchrotron-self-Compton model, presenting a new numerical algorithm to determine the best-fit solution, while in Chapter 7 we present a new stationary lepto-hadronic code, which can be used to model the blazar emission in leptonic, hadronic and mixed scenarios.In Chapter 8 we present the problem of the spectral break observed in the GeV spectrum of 3C 454.3, and we model it consistently in an external-inverse-Compton scenario.Finally we present a perspective for the detection of high-redshift sources with the future telescope CTA (Appendix A).
Active Galactic Nuclei
| Author | : Volker Beckmann |
| Publisher | : John Wiley & Sons |
| Total Pages | : 390 |
| Release | : 2013-08-29 |
| Genre | : Science |
| ISBN | : 352766680X |
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)
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 |
A comprehensive introduction to the theory underpinning our study of active galactic nuclei and the ways we observe them.
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 |
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.
High Energy Astrophysics
| Author | : Thierry J.-L. Courvoisier |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 333 |
| Release | : 2012-10-02 |
| Genre | : Science |
| ISBN | : 3642309704 |
High-energy astrophysics has unveiled a Universe very different from that only known from optical observations. It has revealed many types of objects in which typical variability timescales are as short as years, months, days, and hours (in quasars, X-ray binaries, etc), and even down to milli-seconds in gamma ray bursts. The sources of energy that are encountered are only very seldom nuclear fusion, and most of the time gravitation, a paradox when one thinks that gravitation is, by many orders of magnitude, the weakest of the fundamental interactions. The understanding of these objects' physical conditions and the processes revealed by high-energy astrophysics in the last decades is nowadays part of astrophysicists' culture, even of those active in other domains of astronomy. This book evolved from lectures given to master and PhD students at the University of Geneva since the early 1990s. It aims at providing astronomers and physicists intending to be active in high-energy astrophysics a broad basis on which they should be able to build the more specific knowledge they will need. While in the first part of the book the physical processes are described and derived in detail, the second part studies astrophysical objects in which high-energy astrophysics processes are crucial. This two-pronged approach will help students recognise physical processes by their observational signatures in contexts that may differ widely from those presented here.
