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Добірка наукової літератури з теми "Fanaroff-Riley class I"

Автор: Grafiati
Опубліковано: 14 березня 2023

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Статті в журналах з теми "Fanaroff-Riley class I"

1

V Bicknell, Geoffrey. "Extragalactic Radio Sources and the Role of Relativistic Jets." Australian Journal of Physics 47, no. 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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2

Meier, D. L., P. Godon, S. Edgington, D. G. Payne, and 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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3

Maslej-Krešňáková, Viera, Khadija El Bouchefry, and 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, no. 1 (May 17, 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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4

Laing, R. A., D. Guidetti, A. H. Bridle, P. Parma, and M. Bondi. "Deep imaging of Fanaroff-Riley Class I radio galaxies with lobes." Monthly Notices of the Royal Astronomical Society 417, no. 4 (August 31, 2011): 2789–808. http://dx.doi.org/10.1111/j.1365-2966.2011.19436.x.

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5

Meier, D. L., P. Godon, S. Edgington, D. G. Payne, and 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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6

Parma, P., H. R. DE RUITER, and 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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Анотація:
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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7

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, no. 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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8

Bicknell, G. V. "Turbulent jets and the energy budget in Fanaroff–Riley class-I radio sources." Canadian Journal of Physics 64, no. 4 (April 1, 1986): 495–500. http://dx.doi.org/10.1139/p86-093.

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Анотація:
There are good reasons, based upon laboratory data and jet morphology, for believing that the jets in Fanaroff–Riley class-I radio sources are turbulently expanding and decelerating owing to the related entrainment. This provides a simple explanation for the usual slow decline of jet-surface brightness in class-I radio sources. A turbulent jet model in which the velocity variation is inferred from the spreading rate is presented and applied to the main jet in NGC 315. Besides providing a reasonable fit to the surface-brightness variation, the model provides the following simple explanation for the collimation behaviour of this jet. Initially, the jet is turbulent but becomes nonturbulent owing to the effect of an increasing Mach number and a favourable pressure gradient causing the jet to collimate. As the pressure flattens out to the background pressure, the jet becomes turbulent again and starts to re-expand. Various implications of the energy budget for the estimation of jet velocity and density are examined, and further implications of the model are discussed.
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9

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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10

Jones, Paul A., and Ben D. Lloyd. "FR I Jets in Southern Radio Galaxies." Symposium - International Astronomical Union 175 (1996): 143–44. http://dx.doi.org/10.1017/s0074180900080347.

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Анотація:
Sources flagged as extended or multiple in the Molonglo Reference Catalogue (MRC, Large et al. 1981, 1991), south of δ = −30°, were observed with the Molonglo Observatory Synthesis Telescope (MOST) with a resolution of 44 arcsec at 843 MHz (Jones and McAdam 1992) to give a sample of 193 southern extended sources. Optical identifications were made using the UKST bJ sky survey. We are now using the Australia Telescope Compact Array (ATCA) near Narrabri in Australia to study a subsample of Fanaroff-Riley class I radio galaxies and fit models to the jets.
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Дисертації з теми "Fanaroff-Riley class I"

1

Lloyd, Ben David, University of Western Sydney, and Faculty of Science and Technology. "Jets in Fanaroff-Riley class I radio galaxies." THESIS_FST_XXX_Lloyd_B.xml, 1997. http://handle.uws.edu.au:8081/1959.7/258.

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Анотація:
Presented here are observations, analysis and interpretation of five Fanaroff-Riley class I radio galaxies. Total intensity and polarised emission was observed in each source at 6 and 3 cm at angular resolutions of 16 to 2 arc seconds. These sources have a flux density greater than 1 Jy at 843 MHz, are 10-30 arc minutes in total angular extent, have redshifts between 0.011 and 0.035, are south of declination –43 degrees and have bright prominent jet structure. Images of the distribution of total intensity, polarised intensity and magnetic field configuration are presented and analysed. Physical properties in the jets and lobe are estimated using a number of different techniques. The observations have revealed a wide variety of structures, which imply many types of physical processes occurring in these sources, and different types of environments the jets travel through. The surface brightness distribution of some FR I radio galaxies with some characteristics of FR II galaxies are found to be consistent with the jets traveling through flat pressure gradients possibly caused by the presence of a cocoon surrounding the source. Analytical model imply jets with Mach numbers of 1-5, and jet velocities of approximately 1,000-20,000 km s-1 along most of the jets but mildly relativistic velocities 0.1-0.5c are indicated by Doppler boosting models at the base of most of the jets
Doctor of Philosophy (PhD)
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2

Lloyd, Ben David. "Jets in Fanaroff-Riley class I radio galaxies." Thesis, 1997. http://handle.uws.edu.au:8081/1959.7/258.

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Анотація:
Presented here are observations, analysis and interpretation of five Fanaroff-Riley class I radio galaxies. Total intensity and polarised emission was observed in each source at 6 and 3 cm at angular resolutions of 16 to 2 arc seconds. These sources have a flux density greater than 1 Jy at 843 MHz, are 10-30 arc minutes in total angular extent, have redshifts between 0.011 and 0.035, are south of declination –43 degrees and have bright prominent jet structure. Images of the distribution of total intensity, polarised intensity and magnetic field configuration are presented and analysed. Physical properties in the jets and lobe are estimated using a number of different techniques. The observations have revealed a wide variety of structures, which imply many types of physical processes occurring in these sources, and different types of environments the jets travel through. The surface brightness distribution of some FR I radio galaxies with some characteristics of FR II galaxies are found to be consistent with the jets traveling through flat pressure gradients possibly caused by the presence of a cocoon surrounding the source. Analytical model imply jets with Mach numbers of 1-5, and jet velocities of approximately 1,000-20,000 km s-1 along most of the jets but mildly relativistic velocities 0.1-0.5c are indicated by Doppler boosting models at the base of most of the jets
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Тези доповідей конференцій з теми "Fanaroff-Riley class I"

1

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

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2

Fraija, Nissim. "Hadronic processes as origin of TeV emission in Fanaroff & Riley Class I: Cen A, M87 and NGC1275." In Gamma-Ray Bursts 2012 Conference. Trieste, Italy: Sissa Medialab, 2012. http://dx.doi.org/10.22323/1.152.0131.

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