Broad-line radio galaxies: Old and feeble?

Bemmel, Ilse van; Barthel, P. D.

doi:10.1051/0004-6361:20011348

Cited by 22 publications

(41 citation statements)

References 26 publications

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“…• From the statistical analysis of the 3CRR sample, correlating MFIR luminosities with the AGN power indicator [OIII], we conclude that the dominant heating mechanism 5 Note, however, that the NLRG sample of van Bemmel & Barthel (2001) is heterogeneous and, even with the spatial resolution of the HST, it is difficult to detect near-nuclear dust features in the BLRG because, unlike the NLRG, they have luminous point-like nuclei at optical wavelengths.…”

Section: Discussionmentioning

confidence: 87%

“…However, there is some evidence for mild anisotropy in the [OIII] emission of the -generally higher redshift -BLRG/Q in the 2Jy sample as discussed in detail in D09.However, the displacement for the 2Jy BLRG/Q below the L 70µm vs. L [OIII] correlation is not statistically significant (D09). Such a difference could reflect a change in the properties of the torus and/or the spatial distribution of the NLR gas with the luminosity of the AGN.vanBemmel & Barthel (2001) compared ISO and IRAS photometric properties of 10 BLRG, with those of a heterogeneous sample of 5 NLRG detected by IRAS. They found that 7 of the BLRG objects have warm MFIR colors with continuum spectra peaking around…”

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confidence: 99%

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The Origin of the Infrared Emission in Radio Galaxies. Iii. Analysis of 3crr Objects

Dicken

Tadhunter

Axon

et al. 2010

ApJ

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We present Spitzer photometric data for a complete sample of 19 low redshift (z < 0.1) 3CRR radio galaxies as part of our efforts to understand the origin of the prodigious mid-to far-infrared (MFIR) emission from radio-loud AGN.Our results show a correlation between AGN power (indicated by [OIII]λ5007 emission line luminosity) and 24µm luminosity. This result is consistent with the 24µm thermal emission originating from warm dust heated directly by AGN illumination. Applying the same correlation test for 70µm luminosity against[OIII] luminosity we find this relation to suffer from increased scatter compared to that of 24µm. In line with our results for the higher-radio-frequency-selected 2Jy sample, we are able to show that much of this increased scatter is due to heating by starbursts which boost the far-infrared emission at 70µm in a minority of objects (17−35%). Overall this study supports previous work indicating AGN illumination as the dominant heating mechanism for MFIR emitting dust in the majority of low to intermediate redshift radio galaxies (0.03 < z < 0.7), with the advantage of strong statistical evidence. However, we find evidence that the low redshift broad-line objects (z < 0.1) are distinct in terms of their positions on the MFIR vs.[OIII] correlations.

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Section: Discussionmentioning

confidence: 87%

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confidence: 99%

The Origin of the Infrared Emission in Radio Galaxies. Iii. Analysis of 3crr Objects

Dicken

Tadhunter

Axon

et al. 2010

ApJ

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“…If we extend our sample by including the 4 radio galaxy-quasar pairs which have been observed with ISOPHOT by van Bemmel et al (2000), and have been selected and evaluated along identical lines as ours, we end up with 7 pairs in which both the radio galaxy and the quasar is detected, 3 pairs with only the quasar, and 1 pair with only the radio galaxy being detected. Thus, also the extended sample is in good statistical agreement with the expectation of the unified scheme in its most simple form.…”

Section: Discussionmentioning

confidence: 99%

Dust emission from 3C radio galaxies and quasars: New ISO observations favour the unified scheme

Meisenheimer

Haas

Muller

et al. 2001

A&A

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Abstract. In order to test the unified scheme for luminous radio galaxies and quasars we observed 10 galaxy/quasar pairs from the 3CR catalogue with ISOPHOT at infrared wavelengths between 5 and 180 µm. Each pair was selected such that both the 178 MHz luminosity and the redshift match as close as possible between the radio galaxy and the quasar in order to minimize effects of cosmic evolution. 13 of the 20 sources were detected in at least one waveband. 12 sources show clear evidence of a thermal bump at FIR wavelength, while in the remaining 7 sources the upper limits are still compatible with the presence of luminous dust emission. In agreement with the predictions of the unified scheme, the quasars and galaxies in our sample cannot be distinguished by their observed mid-and far-infrared properties. This is in contrast to the findings on the basis of the IRAS scans which indicated that radio galaxies radiate significantly less mid-to far-infrared emission than quasars. However, the IRAS samples are dominated by low-redshift sources (z < 0.5), while our sample contains several of the most luminous radio galaxies at redshift z 1. The latter have already been suspected to contain a hidden quasar for other reasons, e.g. an extended emission line region aligned with the radio axis. From the ratio between FIR luminosity emitted by dust and the radio power at 178 MHz, we conclude that the radio galaxy/quasar unification might be perfectly valid for the most luminous 3C sources at high redshift (z > ∼ 0.8). At lower redshifts (z < 0.5), however, some of the lobe-dominated FRII radio galaxies contain active nuclei which emit less UV-optical continuum than the quasars of similar radio power. As this division is mainly a function of redshift and less one of absolute radio power, we suggest that it is caused by the evolution of the nuclear fueling rate with cosmic epoch. In order to quantify the deviation from the purely aspect-dependent unified scheme at low redshifts a larger fraction of 3C radio galaxies has to be observed at mid-to far-infrared wavelengths with sensitivities which suffice to yield secure detections rather than upper limits.

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“…PKS0945+07. This object lies below the correlation, and is an example of an object with an inverted MFIR spectrum that apparently lacks a cool dust component (e.g., Miley et al 1984;van Bemmel & Barthel 2001). 3.…”

Section: Pks0347+05 This Object Lies Behind the Galactic Planementioning

confidence: 97%

THE ORIGIN OF THE INFRARED EMISSION IN RADIO GALAXIES. II. ANALYSIS OF MID- TO FAR-INFRAREDSPITZEROBSERVATIONS OF THE 2JY SAMPLE

Dicken

Tadhunter

Axon

et al. 2009

ApJ

119

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We present an analysis of deep mid-to far-infrared (MFIR) Spitzer photometric observations of the southern 2Jy sample of powerful radio sources (0.05 < z < 0.7), conducting a statistical investigation of the links between radio jet, active galactic nucleus (AGN), starburst activity and MFIR properties. This is part of an ongoing extensive study of powerful radio galaxies that benefits from both complete optical emission line information and a uniquely high detection rate in the far-infrared (far-IR). We find tight correlations between the MFIR and [O iii]λ5007 emission luminosities, which are significantly better than those between MFIR and extended radio luminosities, or between radio and [O iii] luminosities. Since [O iii] is a known indicator of intrinsic AGN power, these correlations confirm AGN illumination of the circumnuclear dust as the primary heating mechanism for the dust producing thermal MFIR emission at both 24 and 70 μm. We demonstrate that AGN heating is energetically feasible, and identify the narrow-line region clouds as the most likely location of the cool, far-IR emitting dust. Starbursts make a major contribution to the heating of the cool dust in only 15%-28% of our targets. We also investigate the orientation dependence of the continuum properties, finding that the broad-and narrow-line objects in our sample with strong emission lines have similar distributions of MFIR luminosities and colors. Therefore our results are entirely consistent with the orientation-based unified schemes for powerful radio galaxies. However, the weak line radio galaxies form a separate class of objects with intrinsically low-luminosity AGNs in which both the optical emission lines and the MFIR continuum are weak.

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Broad-line radio galaxies: Old and feeble?

Cited by 22 publications

References 26 publications

The Origin of the Infrared Emission in Radio Galaxies. Iii. Analysis of 3crr Objects

The Origin of the Infrared Emission in Radio Galaxies. Iii. Analysis of 3crr Objects

Dust emission from 3C radio galaxies and quasars: New ISO observations favour the unified scheme

THE ORIGIN OF THE INFRARED EMISSION IN RADIO GALAXIES. II. ANALYSIS OF MID- TO FAR-INFRAREDSPITZEROBSERVATIONS OF THE 2JY SAMPLE

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