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Bibliographies thématiques / Fanaroff-Riley class II

Littérature scientifique sur le sujet « Fanaroff-Riley class II »

Auteur : Grafiati

Publié le 14 mars 2023

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Articles de revues sur le sujet "Fanaroff-Riley class II"

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V Bicknell, Geoffrey. « Extragalactic Radio Sources and the Role of Relativistic Jets ». Australian Journal of Physics 47, n^o 5 (1994) : 669. http://dx.doi.org/10.1071/ph940669.

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This paper summarises some of the ideas surrounding the role of relativistic jets in radio galaxies and quasars and describes work presented in two recent papers (Bicknell 1994a,b) relating relativistic jets to the Fanaroff~Riley classification of radio galaxies. I conclude with some speculation on the evolutionary connection between Fanaroff~Riley Class I and Class II radio galaxies and the relationship between mergers and radio galaxies, an idea which was discussed at the time of the discovery of Cygnus A and Ccntaurus A.

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Meier, D. L., P. Godon, S. Edgington, D. G. Payne et K. R. Lind. « 11.18. The magnetic switch and the FR I/FR II break ». Symposium - International Astronomical Union 184 (1998) : 491–92. http://dx.doi.org/10.1017/s0074180900085727.

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Maslej-Krešňáková, Viera, Khadija El Bouchefry et Peter Butka. « Morphological classification of compact and extended radio galaxies using convolutional neural networks and data augmentation techniques ». Monthly Notices of the Royal Astronomical Society 505, n^o 1 (17 mai 2021) : 1464–75. http://dx.doi.org/10.1093/mnras/stab1400.

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ABSTRACT Machine-learning techniques have been increasingly used in astronomical applications and have proven to successfully classify objects in image data with high accuracy. The current work uses archival data from the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) to classify radio galaxies into four classes: Fanaroff–Riley Class I (FRI), Fanaroff–Riley Class II (FRII), Bent-Tailed (BENT), and Compact (COMPT). The model presented in this work is based on Convolutional Neural Networks (CNNs). The proposed architecture comprises three parallel blocks of convolutional layers combined and processed for final classification by two feed-forward layers. Our model classified selected classes of radio galaxy sources on an independent testing subset with an average of 96 per cent for precision, recall, and F1 score. The best selected augmentation techniques were rotations, horizontal or vertical flips, and increase of brightness. Shifts, zoom, and decrease of brightness worsened the performance of the model. The current results show that model developed in this work is able to identify different morphological classes of radio galaxies with a high efficiency and performance.

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Bicknell, G. V. « The Relationship of the Fanaroff-Riley Classification of Extragalactic Radio Sources to Jet Physics ». Publications of the Astronomical Society of Australia 6, n^o 2 (1985) : 130–37. http://dx.doi.org/10.1017/s1323358000017926.

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AbstractThe Class I/Class II division of extragalactic radio sources by Fanaroff-Riley is a manifestation of important physical differences existing in radio sources.It is proposed that the division essentially arises from the differing Mach numbers in Class I and Class II jets. The low Mach number, Class I jets are susceptible to turbulence, are decelerated by entrainment of the surrounding medium and maintain an anomalously high surface brightness as a result. The high Mach number, Class II jets are less turbulent and remain supersonic, produce high pressure shocks along their lengths and terminate via a strong shock against the IGM.An analysis of the energy balance in both types of source reveals jet velocities of the order of 5-10,000 km s-1 for Class I jets and mildly relativistic velocities for Class II jets.The important rôle of optical and X-ray observations in determining the gravitational field of pressure distribution in radio galaxies will be discussed with examples given of NGC1399 and IC4296.

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Meier, D. L., P. Godon, S. Edgington, D. G. Payne et K. R. Lind. « The Magnetic Switch as the Origin of the FR I/FR II Break ». International Astronomical Union Colloquium 164 (1998) : 51–52. http://dx.doi.org/10.1017/s0252921100044481.

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AbstractWe propose that the Fanaroff & Riley division between class I and class II radio sources has its origins in the coronae of magnetized accretion disks around black holes. The “magnetic switch”, an effect that critically controls the speed of jets produced by such disks, can explain both qualitative and quantitative differences in the properties of the two classes. These include why morphology and jet speed are functions of radio power and why the division between the two classes is a strong function of galaxy optical luminosity.

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Huarte-Espinosa, M., M. Krause et P. Alexander. « Interaction of Fanaroff-Riley class II radio jets with a randomly magnetized intracluster medium ». Monthly Notices of the Royal Astronomical Society 418, n^o 3 (14 novembre 2011) : 1621–39. http://dx.doi.org/10.1111/j.1365-2966.2011.19545.x.

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Parma, P., H. R. DE RUITER et R. Fanti. « Low Luminosity Radio Galaxies ». Symposium - International Astronomical Union 175 (1996) : 137–42. http://dx.doi.org/10.1017/s0074180900080335.

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This review talk will deal almost exclusively with the radio aspects of low luminosity radio galaxies, as the other wavelength bands (optical, X, IR) are covered by others during this conference. By low radio luminosity we mean a radio power at 20 cm in the range 1019 to 1024,5 W Hz–1 (Hubble constant of 100, as throughout this talk). At the upper limit occurs the “break” in the radio luminosity (RLF) (Auriemma et al 1977) as well as the transition from Fanaroff -Riley type I to type II (Fanaroff & Riley, 1974). This limitation to weak radio powers does not necessarily imply that such radio sources constitute a homogeneous class of objects; it has been shown by Wrobel & Heeschen (1991) that a number of radio galaxies of very low luminosity have a ratio between far-infrared and radio emission similar to spiral galaxies and this might suggest that these objects are powered by star formation phenomena. Long baseline interferometry is able to pinpoint compact radio nuclei and therefore can distinguish starburst related radio sources from those powered by nuclear activity (see Slee et al 1994).

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Carvalho, Joel C. « On the Age of GPS Radio Sources ». Symposium - International Astronomical Union 159 (1994) : 424. http://dx.doi.org/10.1017/s0074180900176090.

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The GHz-Peaked-Spectrum (GPS) radio sources are galaxies and quasars with compact structures on scales of tens to hundreds of parsecs and spectrum peaking around 1 GHz. Phillips and Mutel (1982) suggested that the double GPS sources (also called compact doubles, CD) are an early stage of the evolution of the classical double sources of Fanaroff-Riley class II type. We have presented a model (Carvalho, 1985) in which we show that the properties of the CD sources are consistent with such a scenario. Their ages would be of the order of 104 yr.

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Macconi, D., E. Torresi, P. Grandi, B. Boccardi et C. Vignali. « Radio morphology–accretion mode link in Fanaroff–Riley type II low-excitation radio galaxies ». Monthly Notices of the Royal Astronomical Society 493, n^o 3 (27 février 2020) : 4355–66. http://dx.doi.org/10.1093/mnras/staa560.

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ABSTRACT Fanaroff–Riley type II (FR II) low-excitation radio galaxies (LERGs) are characterized by weak nuclear excitation on parsec-scales and properties typical of powerful FR IIs (defined as high-excitation radio galaxies, hereafter HERGs/BLRGs) on kiloparsec-scales. Since a link between the accretion properties and the power of the produced jets is expected both from theory and observations, their nature is still debated. In this work, we investigate the X-ray properties of a complete sample of 19 FR II-LERGs belonging to the 3CR catalogue, exploiting Chandra and XMM–Newton archival data. We also analyse 32 FR II-HERGs/BLRGs with Chandra data as a control sample. We compared FR II-LERG and FR II-HERG/BLRG X-ray properties and optical data available in literature to obtain a wide outlook of their behaviour. The low accretion rate estimates for FR II-LERGs, from both X-ray and optical bands, allow us to firmly reject the hypothesis as they are the highly obscured counterpart of powerful FR II-HERGs/BLRGs. Therefore, at least two hypothesis can be invoked to explain the FR II-LERG nature: (i) they are evolving from classical FR IIs because of the depletion of accreting cold gas in the nuclear region, while the extended radio emission is the heritage of a past efficiently accreting activity; and (ii) they are an intrinsically distinct class of objects with respect to classical FR Is/FR IIs. Surprisingly, in this direction, a correlation between accretion rates and environmental richness is found in our sample. The richer the environment is, the more inefficient is the accretion. In this framework, the FR II-LERGs are intermediate between FR Is and FR II-HERGs/BLRGs both in terms of accretion rate and environment.

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Huarte-Espinosa, M., M. Krause et P. Alexander. « 3D magnetohydrodynamic simulations of the evolution of magnetic fields in Fanaroff-Riley class II radio sources ». Monthly Notices of the Royal Astronomical Society 417, n^o 1 (1 août 2011) : 382–99. http://dx.doi.org/10.1111/j.1365-2966.2011.19271.x.

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Actes de conférences sur le sujet "Fanaroff-Riley class II"

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Rachen, Jörg, et Peter L. Biermann. « Ultrahigh-energy cosmic rays from Fanaroff Riley class II radio galaxies ». Dans Particle acceleration in cosmic plasmas. AIP, 1992. http://dx.doi.org/10.1063/1.42713.

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