Author: Peter L. BiermannPublisher:
ISBN:
Category :
Languages : en
Pages : 36
Book Description
Active Galactic Nuclei: Sources for Ultra High Energy Cosmic Rays?
Author: Peter L. BiermannOn the Possible Association of Ultra High Energy Cosmic Rays with Nearby Active Galaxies
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 11
Book Description
Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of cosmic rays (CRs) with energies>57 EeV that suggests a correlation with the positions of active galactic nuclei (AGN) located within H"5 Mpc. However, this analysis does not take into account AGN morphology. A detailed study of the sample of AGN whose positions correlate with the CR events shows that most of them are classified as Seyfert 2 and low-ionization nuclear emission-line region (LINER) galaxies which do not differ from other local AGN of the same types. Therefore, the claimed correlation between the CR events observed by the Pierre Auger Observatory and local active galaxies should be considered as resulting from a chance coincidence, if the production of the highest energy CRs is not episodic in nature, but operates in a single object on long (e"Myr) timescales. Additionally, most of the selected sources do not show significant jet activity, and hence--in the framework of the jet paradigm--there are no reasons for expecting them to accelerate CRs up to the highest energies, H"02° eV, at all. If the extragalactic magnetic fields and the sources of these CRs are coupled with matter, it is possible that the deflection angle is larger than expected in the case of a uniform source distribution due to effectively larger fields. A future analysis has to take into account AGN morphology and may yield a correlation with a larger deflection angle and/or more distant sources. We further argue that Cen A alone could be associated with at least 4 events due to its large radio extent, and Cen B can be associated with more than 1 event due to its proximity to the Galactic plane and, correspondingly, the stronger Galactic magnetic field the ultra high energy CRs (UHECRs) encounter during propagation. If the UHECRs associated with these events are indeed accelerated by Cen A and Cen B, their deflection angles may provide information on the structure of the magnetic field in the direction of these putative sources. Future -ray observations (by, e.g., Gamma-Ray Large Area Space Telescope [GLAST], High Energy Stereoscopic System [HESS]) may provide additional clues to the nature of the accelerators of the UHECRs in the local Universe.
Composition and Origin of Cosmic Rays
Author: M.M. ShapiroPublisher: Springer Science & Business Media
ISBN: 9400971664
Category : Science
Languages : en
Pages : 419
Book Description
Proceedings of the NATO Advanced Study Institute, Ettore Majorana Centre, Erice, Sicily, Italy, June 20-30, 1982
Acceleration and Propagation of Cosmic Rays in High-Metallicity Astrophysical Environments
Author: Ana Laura MüllerPublisher: Springer Nature
ISBN: 3031103068
Category : Science
Languages : en
Pages : 141
Book Description
This thesis addresses the feasibility of the production of ultra-high-energy cosmic rays in starburst galaxies and active galactic nuclei. These astrophysical objects were theoretically proposed as candidate sources a long time ago. Nevertheless, the interest in them has been recently renewed due to the observational data collected by the Pierre Auger Observatory and the Telescope Array. In this work, a comprehensive review of the current status of the research on cosmic rays accelerators is provided, along with a summary of the principal concepts needed to connect these relativistic particles with electromagnetic and neutrino observations in the multi-messenger era. On one hand, the hypothesis of accelerating particles with energies above 1018 eV in starburst superwinds is carefully revisited, taking into account the constraints imposed by the most recent electromagnetic observations. On the other hand, an alternative new model for the gamma emission of the nearby active galaxy NGC 1068 is presented. The implications of the results of these studies are discussed in terms of the contemporary observatories and prospects for future experiments are offered.
Ultra High Energy Cosmic Ray Composition
Author: Nathaniel Peter LongleyPublisher:
ISBN:
Category :
Languages : en
Pages : 282
Book Description
Gamma-ray Large Area Space Telescope
Author: Correlation of the Highest-energy Cosmic Rays with the Positions of Nearby Active Galactic Nuclei
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 33
Book Description
Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of the cosmic rays with the highest energies, which are correlated with the positions of relatively nearby active galactic nuclei (AGN) [1]. The correlation has maximum significance for cosmic rays with energy greater than (almost equal to) 6 x 1019 eV and AGN at a distance less than (almost equal to) 75 Mpc. We have confirmed the anisotropy at a confidence level of more than 99% through a test with parameters specified a priori, using an independent data set. The observed correlation is compatible with the hypothesis that cosmic rays with the highest energies originate from extra-galactic sources close enough so that their flux is not significantly attenuated by interaction with the cosmic background radiation (the Greisen-Zatsepin-Kuzmin effect). The angular scale of the correlation observed is a few degrees, which suggests a predominantly light composition unless the magnetic fields are very weak outside the thin disk of our galaxy. Our present data do not identify AGN as the sources of cosmic rays unambiguously, and other candidate sources which are distributed as nearby AGN are not ruled out. We discuss the prospect of unequivocal identification of individual sources of the highest-energy cosmic rays within a few years of continued operation of the Pierre Auger Observatory.
Cosmic Radiation in Contemporary Astrophysics
Author: M.M. ShapiroPublisher: Springer Science & Business Media
ISBN: 9400954883
Category : Science
Languages : en
Pages : 270
Book Description
This volume is the product of Lecturers in the fourth Course of the International School of Cosmic-Ray Astrophysics held at the Ettore Majorana Center in Erice, Sicily in November, 1984. The Course, devoted to "Cosmic Radiation in Contemporary Astrophysics," was concurrently a NATO-sponsored Advanced Study Institute (ASI). Cosmic-ray research is in a state of ferment. Precise measure ments - some made with instruments aboard sattelites and space probe- have been confronting models and theories with severe constraints. The observations of gamma-ray sources, notably Cyg X-3, at energies up to 16 10 eV, have opened up tantalizing possibilities of direct source iden tification. This ASI was devoted largely to interdisciplinary phenomena in cosmic-ray astrophysics whose understanding requires input from the other channels in astronomy. It explored the ways in which progress in cosmic-ray science might clarify phenomena observed in related disciplines. In trying to achieve this aim, we assembled a staff of lecturers representing various astrophysical specialties, such as radio astronomy, optical astronomy, X-ray astronomy, gamma-ray astronomy, and of course, particle astronomy (i.e., cosmic radiation). Students and other participants were likewise drawn from diverse backgrounds. Vigorous discussions enlivened almost every session.
Cosmic Rays
Author: Very High Energy Phenomena in the Universe
Author: Yannick Giraud-HéraudPublisher: Atlantica Séguier Frontières
ISBN: 9782863322178
Category : Electroweak interactions
Languages : en
Pages : 488
Book Description