Relativistic beaming in the central components of double radio quasars

Kapahi, V. K.; Saikia, D. J.

doi:10.1007/bf02714886

Cited by 92 publications

(55 citation statements)

References 30 publications

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“…R c has indeed been shown to correlate with other orientation-dependent properties both in FRIIs (e.g., Kapahi & Saikia 1982) and FRIs (e.g., Laing et al 1999). We use the parameter R c to test if the luminosities of the optical nuclei L o , are orientation-dependent.…”

Section: The Optical Nuclei In Fri and Frii Radio Galaxiesmentioning

confidence: 98%

Optical nuclei of radio-loud AGN and the Fanaroff-Riley divide

Kharb¹,

Shastri²

2004

A&A

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Abstract. We investigate the nature of the point-like optical nuclei that have been found in the centres of the host galaxies of a majority of radio galaxies by the Hubble Space Telescope. We examine the evidence that these optical nuclei are relativistically beamed, and look for differences in the behaviour of the nuclei found in radio galaxies of the two Fanaroff-Riley types. We also attempt to relate this behaviour to the properties of the optical nuclei in their highly beamed counterparts (the BL Lac objects and radio-loud quasars) as hypothesized by the simple Unified Scheme. Simple model-fitting of the data suggests that the emission may be coming from a non-thermal relativistic jet. It is also suggestive that the contribution from an accretion disk is not significant for the FRI objects and for the narrow-line radio galaxies of FRII type, while it may be significant for the Broad-line objects, and consistent with the idea that the FRII optical nuclei seem to suffer from extinction due to an obscuring torus while the FRI optical nuclei do not. These results are broadly in agreement with the Unified Scheme for radio-loud AGNs.

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Section: The Optical Nuclei In Fri and Frii Radio Galaxiesmentioning

confidence: 98%

Optical nuclei of radio-loud AGN and the Fanaroff-Riley divide

Kharb¹,

Shastri²

2004

A&A

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“…Therefore, the ratio of the core and extended flux densities becomes a beaming indicator (Kapahi & Saikia 1982). We define an analogous parameter R for Seyfert galaxies as…”

Section: Relativistic Beaming In Seyfert Galaxies?mentioning

confidence: 99%

Seyfert Galaxies: Nuclear Radio Structure and Unification

Lal

Shastri

Gabuzda

2011

ApJ

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A radio study of a carefully selected sample of 20 Seyfert galaxies that are matched in orientation-independent parameters, which are measures of intrinsic active galactic nucleus power and host galaxy properties, is presented to test the predictions of the unified scheme hypothesis. Our sample sources have core flux densities greater than 8 mJy at 5 GHz on arcsec scales due to the feasibility requirements. These simultaneous parsec-scale and kiloparsec-scale radio observations reveal (1) that Seyfert 1 and Seyfert 2 galaxies have an equal tendency to show compact radio structures on milliarcsecond scales, (2) the distributions of parsec-scale and kiloparsec-scale radio luminosities are similar for both Seyfert 1 and Seyfert 2 galaxies, (3) there is no evidence for relativistic beaming in Seyfert galaxies, (4) similar distributions of source spectral indices in spite of the fact that Seyferts show nuclear radio flux density variations, and (5) the distributions of the projected linear size for Seyfert 1 and Seyfert 2 galaxies are not significantly different as would be expected in the unified scheme. The latter could be mainly due to a relatively large spread in the intrinsic sizes. We also find that a starburst alone cannot power these radio sources. Finally, an analysis of the kiloparsec-scale radio properties of the CfA Seyfert galaxy sample shows results consistent with the predictions of the unified scheme.

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“…Assuming that the jets are intrinsically symmetric and any apparent asymmetry is due to the difference in light travel times between the two sides (e.g., Longair & Riley 1979;Kapahi & Saikia 1982) and using the relation Q = (1 + β cos θ)/(1 − β cos θ), an arm-length ratio of 1.1 would give a β cos θ of 0.047 or θ = 62 degrees relative to the line of sight for β = 0.1 (e.g., Bridle & Perley 1984).…”

Section: Projection Effectsmentioning

confidence: 99%

“…For sources lying at small angles to line of sight, intrinsic misalignment between the jet and counter-jet appears to get amplified (e.g., Kapahi & Saikia 1982). The observed misalignment (ζ) is related to the intrinsic misalignment (ζ int ), by sin(θ) = tan(ζ int )/ tan(ζ), for the simplified case in which the azimuth of the jet bending is 90…”

Section: Projection Effectsmentioning

confidence: 99%

Physical properties of very powerful FRII radio galaxies

O’Dea

Daly

Kharb

et al. 2008

A&A

116

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Aims. We estimate the ages and physical properties of powerful radio galaxies.Methods. An analysis of new multi-wavelength VLA observations of eleven very powerful classical double (FRIIb) radio galaxies with redshifts between 0.4 and 1.3 is presented. We estimate ages and velocities for each side of each source. The eleven new sources are combined with previously studied samples and the characteristics of the full sample of 31 sources are studied; the full sample includes sources with redshifts between 0.056 and 1.79, and core-hot spot sizes of about 30 to 400 kpc. Results. The velocities are independent of core-hotspot separation, suggesting the rate of growth of a given source is roughly constant over the source lifetime. We combine the rate of growth, width, and pressure of a source to study the beam power, lifetime, energy, and ambient gas density using standard methods previously applied to smaller samples. Typical beam powers are in the range from 10 44 to 10 46 erg/s; we show that this quantity is insensitive to assumptions regarding minimum energy conditions. The beam powers are independent of core-hotspot separation suggesting that the beam power of a given source is roughly constant over the source lifetime. Typical total source lifetimes are found to be about a few ×(10 6 −10 7 ) years, and typical total outflow energies (E/c 2 ) are found to be about 5 × (10 5 −10 6 ) M . Ambient gas densities are found to decrease with increasing core-hotspot distance, but have no redshift dependence. Overall, the results obtained with the sample of 31 sources studied here are consistent with those obtained earlier with smaller samples.

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Relativistic beaming in the central components of double radio quasars

Cited by 92 publications

References 30 publications

Optical nuclei of radio-loud AGN and the Fanaroff-Riley divide

Optical nuclei of radio-loud AGN and the Fanaroff-Riley divide

Seyfert Galaxies: Nuclear Radio Structure and Unification

Physical properties of very powerful FRII radio galaxies

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