On the FR I/FR II Dichotomy in Powerful Radio Sources: Analysis of Their Emission-Line and Radio Luminosities

Zirbel, Esther; Baum, Stefi A.

doi:10.1086/175984

Cited by 184 publications

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“…Only in the case of 3C 449, the source with the steepest observed spectrum, does this significantly affect the effective observing wavelength and the estimate of the flux. (Giovannini et al 1988;Zirbel & Baum 1995). Cols.…”

Section: Resultsmentioning

confidence: 99%

The Nuclei of Radio Galaxies in the Ultraviolet: The Signature of Different Emission Processes

Chiaberge

Macchetto

Sparks

et al. 2002

ApJ

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We have studied the nuclei of 28 radio galaxies from the 3CR sample in the UV band. Unresolved nuclei (central compact cores: CCCs) are observed in 10 of the 13 FR I galaxies, and in five of the 15 FR II galaxies. All sources that do not have a CCC in the optical do not have a CCC in the UV. Two FR I galaxies (3C 270 and 3C 296) have a CCC in the optical but do not show the UV counterpart. Both of them show large dusty disks observed almost edge-on, possibly implying that they play a role in obscuring the nuclear emission. We have measured optical-UV spectral indices o,UV between $0.6 and $7.0 (F / À ). Broad-line radio galaxies have the flattest spectra, and their values of o,UV are also confined to a very narrow range. This is consistent with radiation produced in a geometrically thin, optically thick accretion disk. On the other hand, FR I nuclei, which are most plausibly originated by synchrotron emission from the inner relativistic jet, show a wide range of o,UV . There is a clear trend with orientation in that sources observed almost edge-on or with clear signs of dust absorption have the steepest spectra. These observations imply that in FR I galaxies, obscuration can be present, but the obscuring material is not in a '' standard '' geometrically thick torus. The most striking difference between these absorbing structures and the classic active galactic nucleus '' tori '' resides in the lower optical depth of the FR I galaxy obscuring material.

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Section: Resultsmentioning

confidence: 99%

The Nuclei of Radio Galaxies in the Ultraviolet: The Signature of Different Emission Processes

Chiaberge

Macchetto

Sparks

et al. 2002

ApJ

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“…In addition to host galaxy magnitude and environments, FR Is and FR IIs differ in optical emission lines (e.g. Zirbel & Baum 1995). As in the case of blazars, Ghisellini & Celotti (2001) introduced that the division between FR Is and FR IIs actually reflected a systematic difference in accretion rate.…”

Section: Introductionmentioning

confidence: 99%

From the ‘blazar sequence' to unification of blazars and radio galaxies

Xiong

Zhang

Bai

et al. 2015

Monthly Notices of the Royal Astronomical Society

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Based on a large Fermi blazar sample, the blazar sequence (synchrotron peak frequency ν peak versus synchrotron peak luminosity L peak ) is revisited. It is found that there is significant anti-correlation between ν peak and L peak for blazars. However, after being Doppler corrected, the anti-correlation disappears. The jet cavity power (P jet ) is estimated from extended radio luminosity. So it is free of beaming effect. We find that there are significant anti-correlations between P jet and beam-corrected ν ′ peak for both blazars and radio galaxies, which supports the blazar sequence and unification of blazars and radio galaxies (an alternative relationship is the correlation between jet power and γ-ray photon index).

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“…Several authors claim that it is connected with transition of the intrinsically supersonic jet to transonic/subsonic flow that is being decelerated due to entrainment of thermal plasma in the innermost region of the host galaxy (e.g: Komissarov 1994; Bowman et al 1996;Bicknell 1995;Kaiser & Alexander 1997). A second hypothesis links aberration in morphology with a more profound issue of the central engine (Meier et al 1997;Zirbel & Baum 1995) or the jet itself (Reynolds et al 1996;Ghisellini & Celotti 2001). Last but not least, the scheme attributes FR I/FR II dichotomy to the intergalactic medium, which together with jet power shapes the object morphology (Gopal-Krishna 1991;Gopal-Krishna et al 1996).…”

Section: Introductionmentioning

confidence: 99%

Orientation of the cores of hybrid morphology radio sources

Ceglowski

Gawroński

Kunert-Bajraszewska

2013

A&A

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Aims. The FR I/FR II dichotomy is a much debated issue in the astrophysics of extragalactic radio sources. Study of the properties of HYbrid MOrphology Radio Sources (HYMORS) may bring crucial information and lead to a step forward in understanding the origin of FR I/FR II dichotomy. HYMORS are a rare class of double-lobed radio sources where each of the two lobes clearly exhibits a different FR morphology. This article describes follow-up high resolution VLBA observations of the five discovered by us HYMORS. The main aim of the observations was to answer the questions of whether the unusual radio morphology is connected to the orientation of objects towards the observer. Methods. The milliarcsecond-scale structures are good probes of the galactic medium, the possible asymmetries, and orientation of the central engines of the sources. We obtained the high resolution radio maps of five hybrid radio morphology objects with the VLBA at C-band and L-band. Results. The cores of all five sources have been detected at both radio bands. Two of them revealed milliarcsecond core-jet structures, the next two objects showed hints of parsec-scale jets, and the last one remained point-like at both frequencies. Conclusions. We compared properties of observed milliarcsecond structures of hybrid sources with the larger scale ones previously detected with the VLA. We find that on both scales the fluxes of their central components are similar, which may indicate the lack of additional emission in the proximity of the nucleus. This suggests that jets present on the ∼1−10 kpc scale in those objects are FR II-like. When possible, the detected core-jet structures were used for estimating the core's spatial orientation. The result is that neither the FR I-like nor the FR II-like side is preferred, which may suggest that no specific spatial orientation of HYMORS is required to explain their radio morphology. Their estimated viewing angles indicate they are unbeamed objects. The 178/151 MHz luminosity of observed HYMORS exceed the traditional FR I/FR II break luminosity, indicating they have radio powers similar to FR IIs.

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On the FR I/FR II Dichotomy in Powerful Radio Sources: Analysis of Their Emission-Line and Radio Luminosities

Cited by 184 publications

References 0 publications

The Nuclei of Radio Galaxies in the Ultraviolet: The Signature of Different Emission Processes

The Nuclei of Radio Galaxies in the Ultraviolet: The Signature of Different Emission Processes

From the ‘blazar sequence' to unification of blazars and radio galaxies

Orientation of the cores of hybrid morphology radio sources

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