Optical and radio properties of 4C galaxies

Wilkinson, A.; Hine, R. G.; Sargent, W. L. W.

doi:10.1093/mnras/196.3.669

Cited by 6 publications

(2 citation statements)

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“…Data from Burns and Gregory (1982), image supplied by J. O. Burns. similarly correlated with the source structure (Hine and Longair, 1979;Wilkinson, Hine, and Sargent, 1981). Most extended sources are now known to be triple rather than double as they were first described.…”

Section: Theorymentioning

confidence: 85%

Theory of extragalactic radio sources

1984

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Powerful extragalactic radio sources comprise two extended regions containing magnetic field and synchrotron-emitting relativistic electrons, each linked by a jet to a central compact radio source located in the nucleus of the associated galaxy. These jets are collimated streams of plasma that emerge from the nucleus in opposite directions, along which flow mass, momentum, energy, and magnetic flux. Methods of using the observations diagnostically to infer the pressures, densities, and fluid velocities within jets are explained. The jets terminate in the extended radio components, where they interact strongly with the surrounding medium through a combination of shock waves and instabilities. Jets may expand freely, be confined by external gas pressure, or be pinched by toroidal magnetic fields. Shear flows are known to be Kelvin-Helmholtz unstable and thus may be responsible for some of the observed oscillation of jets about their mean directions and for creating the turbulence and shock waves needed to accelerate the relativistic electrons. Larger-scale bending may be caused by changes in the jet axis within the nucleus, gravitational interaction of the radio galaxy with a companion galaxy, or rapid motion of the source through dense intergalactic gas. The compact radio sources also exhibit a jet morphology and contain more direct clues as to the origins of jets; in particular, the variations sometimes observed imply bulk flows that are relativistic. It is widely believed that nuclear activity is ultimately ascribable to gas accreting onto a massive black hole. The accretion can proceed in several different fashions, depending upon whether or not the gas has angular momentum and whether or not the radiation emitted is sufficiently intense to influence the dynamics of the flow. Several distinct mechanisms for jet production in the context of black holes have been proposed. (Alternative mechanisms involving dense star clusters and massive spinning stars are also reviewed. ) Supersonic jets may be collimated along the spin axis of a gas cloud surrounding the source of the lighter jet gas. Magnetic fields may be crucial in collimating jets, especially if they are wrapped around the jet by orbiting gas and can thereby collimate the outflow through the pinch effect. In fact, the spin energy of the black hole could also be extracted by magnetic torques, in which case the jet would contain electrons and positrons and carry a large electromagnetic Poynting flux. Statistical investigations of active galaxies also furnish valuable information on their nature and evolutionary behavior. The formation of particular kinds of sources appears to be correlated with environmental effects and cosmic epoch. In addition, the brightest compact radio sources on the sky, which probably involve relativistic motion, may be intrinsically faint objects beamed in our direction. There is now compelling evidence for the continuous fueling of extragalactic radio sources through jets emerging from the nucleus of the associated galaxy. The morpho...

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Section: Theorymentioning

confidence: 85%

Theory of extragalactic radio sources

1984

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“…Kristian, Sandage, andWestphal 1974, 1978;Laing et al 1978;Riley, Longair, and Gunn 1980;Gunn et al 1981) even at very faint optical magnitudes. These faint, presumably distant 3CR sources all have very high radio luminosities, and this property correlates with the long-known propensity of the central optical galaxy to show strong (nuclear) emission lines (Smith, Spinrad, and Smith 1976;Hine and Longair 1979;Wilkinson, Hine, and Sargent 1981).…”

Section: Introduction Observational Philosophy Data Presentationmentioning

confidence: 61%

Redshifts and spectroscopy of very distant radio galaxies with strong emission lines

Spinrad¹

1982

PASP

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The optical spectra of six newly observed 3CR radio galaxies, mostly with redshifts near unity, are unique with enormously strong [O II] emission. The observed equivalent widths of A 0 3727 range from 100 Á to about 2000 Á, and the luminosity in this single line exceeds 10 10 L© in the extreme case of 3C 368 (z = 1.13).The coarse line ratios and linewidths of [Oïl], [NeIII], [Ne v], and the occasional presence of MgII suggest a shock-excitation model for the gas in 3C 368, 3C 184, 3C 175.1, and possibly 3C 34. 3C 356 and 3C 280 have moderately strong [Nev] and may require a uv power-law continuum. A rough inverse-correlation exists between the emission lines velocity width and relative strengths of the high-ionization [Nev] and the strong low-ionization [Oil] lines. The energetics of a shock-origin for the low-ionization lines may be difficult unless a large reservoir of neutral gas is available.The shape of the thermal continuum of 3C 280 has been measured-this galaxy consists of old stars with a spectral distribution consistent with Bruzual models which have a last epoch of star formation ceasing at 2 > 4.We note that these very luminous radio galaxies are the ones which experience rapid evolution needed to explain the radio source counts. They are about 300 times more abundant (per unit co-moving volume) at 2 ~ 1.0 than locally (z ~ 0.1). Perhaps this rapid evolutionary turnoff at the present epoch represents some efficient utilization and later unavailability of an external fuel source, much more commonly available to gE galaxies a half-Hubble-time ago.

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Extended Emission-Line Regions as Probes of Nuclear Activity in Galaxies

Wilson¹

1992

Physics of Active Galactic Nuclei

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Optical and radio properties of 4C galaxies

Cited by 6 publications

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Theory of extragalactic radio sources

Theory of extragalactic radio sources

Redshifts and spectroscopy of very distant radio galaxies with strong emission lines

Extended Emission-Line Regions as Probes of Nuclear Activity in Galaxies

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