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| Author | : Daniil Nekrassov |
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| Total Pages | : 0 |
| Release | : 2010 |
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The High Energy Stereoscopic System, H.E.S.S., is an array of four imaging atmosphericCherenkov telescopes, located in the Khomas highlands of Namibia, designed for the exploration of very high-energy (E> 100 GeV) gamma-ray emission in the universe, arising in non-thermal processes. Its location in the southern hemisphere renders sensitive observations of a large region of the Galactic Plane possible. In particular, a deep exposure of the Galactic Center region allows detailed studies of the observed emission, helping to identify the sources of the radiation and the physics processes at play. In this thesis, new methods are developed to study both the morphological and spectral properties of diffuse very high-energy gamma-ray emission from the Galactic Center region. Assuming that the radiation originates from hadronic interactions of diffusing cosmic rays with the ambient matter, this study helps to constrain the parameter space of cosmic-ray diffusion in the Galactic Center region. The second part of this work introduces new methods to search for signals of Dark Matter annihilations, putting upper-limits on the production of spectral line features in the H.E.S.S. Galactic Center data. Finally, an upper-limit on the total annihilation cross-section of Dark Matter particles is derived.
| Author | : Lucia Rinchiuso |
| Publisher | : |
| Total Pages | : 0 |
| Release | : 2019 |
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The H.E.S.S. (High Energy Spectroscopic System) experiment is an array of five Cherenkov telescopes that observe the sky in gamma-rays from about 100 GeV up to several ten TeV.Gamma rays are produced in violent non-thermal phenomena in the Universe in the neighborhood of pulsars, supernovae, black holes, ..., and could also be produced by the annihilation of dark matter particles.Numerous cosmological and astrophysical probes suggest that 85% of the total matter budget in the Universe is of unknown origin. This component of matter known as dark matter is non baryonic and could consist of yet undiscovered particles which privileged candidates are arguably massive particles with electroweak couplings with ordinary matter (WIMPs).Dark matter particles may annihilate into Standard Model particles in dense regions of the Universe. Among the annihilation products are photons which detection at high energy with ground-based Cherenkov telescopes could bring unique information on the nature of the dark matter.H.E.S.S. observes dark-matter-dense regions of the sky such as the Galactic Center and dwarf galaxy satellites of the Milky Way. A study on the interpretation of an excess of gamma-rays detected by H.E.S.S. at the Galactic Center in terms of acceleration of protons by a population of unresolved millisecond pulsars is performed.10 years of observations of the Galactic Center with the four-telescope H.E.S.S.-I array, five years of data taking towards the Galactic Center region with the full H.E.S.S.-II array and a two-years dataset towards newly discovered dwarf spheroidal galaxies are analyzed. The search for dark matter annihilation signals towards these targets provided the strongest limits so far on dark matter annihilation cross section in gamma rays of TeV energies. The potential of dark matter detection with the upcoming Cherenkov Telescope Array (CTA) towards the inner Galactic halo are studied. They may annihilate into Standard Model particles in dense regions of the Universe. Among the annihilation products are high energy photons. The detection of these photons with ground-based Cherenkov telescopes may reveal the nature of the dark matter. H.E.S.S. have observed some dark-matter-dense regions of the sky likethe Galactic Center and dwarf galaxies satellites of the Milky Way. In this work 10 years of observations of the Galactic Center with the four-telescopes H.E.S.S.-I array, five years of data taking towards the Galactic Center region with the full H.E.S.S.-II array and a two-years dataset towards newly discovered dwarf spheroidal galaxies are analyzed. The searches for dark matter annihilation signals towards these targets produced the strongest limits so far on dark matter annihilation cross section in gamma rays of TeV energies.Perspectives of dark matter detection with the future array CTA (Cherenkov Telescope Array) towards the inner Galactic halo are also discussed. A study on the interpretation of an excess of gamma-rays detected by H.E.S.S. at the Galactic Center in terms of acceleration of protons by a population of unresolved millisecond pulsars complements the dark matter searches.
| Author | : Aion Viana |
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| Total Pages | : 0 |
| Release | : 2012 |
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This thesis presents a series of data analysis and phenomenological studies on two main subject of the y-ray astronomy: the indirect searches of dark matter, and the study of the Galactic Center region with the H.E.S.S. telescope array. The indirect dark matter searches focus on the study of two classes of targets: dwarf galaxies and galaxy clusters. A detailed study of the H.E.S.S. observations towards the Sculptor and Carina dwarf galaxies, and towards the Fornax galaxy cluster are presented. In the absence of a significant signal coming from these object, constraints on the annihilation cross section of dark matter particle candidates are derived. The current H.E.S.S. dark matter constraints towards the Sagittarius are updated in light of recent realistic dark matter halo models. A prospect on the sensitivity of the future generation of Cherenkov telescopes, Le. CTA (Cherenkov Telescope Array), for the detection of a dark matter annihilation signal and conventional y-ray emissions is also given. The second subject of this thesis provides a detailed analysis of the very high energy y-ray data from the Galactic Center region observed by the H.E.S.S. experiment throughout the 2004-2011 period. The analysis and spectral reconstruction of the central source and the diffuse emission around this regioi are presented. A spectral subtraction of the diffuse emission contribution to the HESS J1745-2 spectral is performed and allows to recover the intrinsic central source spectrum. The spectra morphology of the diffuse emission region suggests the possibility of various accelerators being responsible for the observed emission.
| Author | : Vlado Valkovic |
| Publisher | : CRC Press |
| Total Pages | : 447 |
| Release | : 2021-11-09 |
| Genre | : Science |
| ISBN | : 1000470806 |
The primary purpose of this book is to prepare the ground for coordinated efforts aiming to answer the question: where and when life originated. The appearance of life involves three successive stages: i) the formation of chemical elements and their combination to simple molecules, which is the concern of physicists; ii) the evolution of organized complexity in biomolecules and their reactions, which falls within the field of chemistry; iii) the onset of Darwinian evolution after the appearance of the first cell-like structure, which is studied by biologists. This book focuses on the first two steps of this process with chapters exploring topics such as chemical element abundances; galaxies, galactic magnetic fields and cosmic rays; galactic chemical evolution. Key Features: Contains extensive lists of reference and additional reading. Includes new hypotheses concerning the origin of life. Combines consideration from nuclear physics, astrophysics, astro- and geochemistry. Despite its interdisciplinary nature, this book remains accessible to nonexperts, and would be a valuable companion for both experts and laypeople.
| Author | : Marco Maria Massai |
| Publisher | : World Scientific |
| Total Pages | : 251 |
| Release | : 2007 |
| Genre | : Nature |
| ISBN | : 9812709657 |
The research program in gamma-ray astronomy focuses on increasing our knowledge of the nature and origin of galactic and extragalactic gamma rays, and understanding high-energy processes in the Sun, celestial objects, interstellar medium, and extragalactic space. This book not only provides an overview of the latest research and future plans for space-borne and ground-based experiments dedicated to the observation of the gamma-ray sky, but also addresses the topic of variable gamma-ray sources from the perspective of their identification and counterparts at different wavelengths. It further gives an overview of the theory related to the most qualified emission processes that take place in these sources and of the nature of their variability. Sample Chapter(s). Integral: 4 Years in Orbit (767 KB). Contents: The Suzaku Mission (K Yamaoka); Gamma-Ray Astrophysics with AGILE (F Longo et al.); The GLAST Mission (J E McEnery); Recent Results from CANGAROO (M Mori); VERITAS: Status and Performance (J Holder); Gamma Ray Pulsars in the GLAST Era (M Razzano); Supernovae and Gamma-Ray Burst (M Della Valle); Solving GRBs and SGRs Puzzles by Precessing Jets (D Fargion et al.); Multiwavelength Observations and Theories of Blazars (G Tosti); Gamma Ray Bursts (L Amati); X-Rays and GeV Flares in GRB Light Curves (A Galli et al.); The Online Monitor for the GLAST Calibration Unit Beam Test (L Baldini et al.); Gamma-Ray Burst Physics with GLAST (N Omodei); The Global Fit Approach to Time-Resolved Spectroscopy of GRBs (A Chernenko); and other papers. Readership: Gamma-ray astronomers; astrophysicists; students and researchers involved in gamma-ray astronomy, both theoretical and experimental; researchers in the development of new gamma-ray detectors.
| Author | : The Cta Consortium |
| Publisher | : World Scientific |
| Total Pages | : 365 |
| Release | : 2018-12-31 |
| Genre | : Science |
| ISBN | : 9813270101 |
This book summarizes the science to be carried out by the upcoming Cherenkov Telescope Array, a major ground-based gamma-ray observatory that will be constructed over the next six to eight years. The major scientific themes, as well as core program of key science projects, have been developed by the CTA Consortium, a collaboration of scientists from many institutions worldwide.CTA will be the major facility in high-energy and very high-energy photon astronomy over the next decade and beyond. CTA will have capabilities well beyond past and present observatories. Thus, CTA's science program is expected to be rich and broad and will complement other major multiwavelength and multimessenger facilities. This book is intended to be the primary resource for the science case for CTA and it thus will be of great interest to the broader physics and astronomy communities. The electronic version (e-book) is available in open access.
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| Total Pages | : 520 |
| Release | : 2005 |
| Genre | : Cosmic rays |
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| Author | : Josep M. Paredes |
| Publisher | : Springer Science & Business Media |
| Total Pages | : 496 |
| Release | : 2007-07-17 |
| Genre | : Science |
| ISBN | : 1402061188 |
This book provides a theoretical and observational overview of the state of the art of gamma-ray astrophysics, and their impact and connection with the physics of cosmic rays and neutrinos. With the aim of shedding new and fresh light on the problem of the nature of the gamma-ray sources, particularly those yet unidentified, this book summarizes contributions to a workshop that continues today.
| Author | : Fulvio Melia |
| Publisher | : Princeton University Press |
| Total Pages | : 324 |
| Release | : 2007 |
| Genre | : Science |
| ISBN | : 9780691131290 |
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