Emission lines and optical continuum in low-luminosity radio galaxies

Wills, K. A.; Morganti, Raffaella; Tadhunter, C. N.; Robinson, T. G.; Villar-Martı́n, M.

doi:10.1111/j.1365-2966.2004.07195.x

Cited by 77 publications

(114 citation statements)

References 52 publications

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“…Morganti et al (1992) extended the line-radio connection towards lower radio luminosities considering sources from the B2 sample, predominantly FR I, noting a flattening in the correlation. This result is supported also by the analysis by Zirbel & Baum (1995), who also report that FR II sources produce about 5−30 times more emission line luminosity than FR I for the same total radio power (see also Tadhunter et al 1998;Wills et al 2004).…”

Section: O Iii]/[o Ii] Line Ratiosupporting

confidence: 75%

An optical spectroscopic survey of the 3CR sample of radio galaxies withz$\mathsf{<}$ 0.3

Buttiglione¹,

Capetti

Celotti³

et al. 2010

A&A

257

390

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In a previous paper we presented a homogeneous and 92% complete optical spectral dataset of the 3CR radio sources with redshift <0.3. Here we use the emission line measurements to explore the spectroscopic properties of the sample. The 3CR sources show a bimodal distribution of excitation index, a new spectroscopic indicator that measures the relative intensity of low and high excitation lines. This unveils the presence of two main sub-populations of radio-loud AGN to which we refer to, following previous studies, as high and low excitation galaxies (HEG and LEG, respectively). In addition to the two main classes, we find one source with a spectrum typical of star forming galaxies, and 3 objects of extremely low level of excitation. All broad-line objects are HEG from the point of view of their narrow emission line ratios and all HEG are FR II radio-galaxies with log L 178 [erg s −1 ] > ∼ 32.8. Conversely LEG cover the whole range of radio power encompassed by this 3CR subsample (30.7 < ∼ log L 178 < ∼ 35.4) and they are of both FR I and FR II type. The brightest LEG are all FR II. HEG and LEG obey to two (quasi) linear correlations between the optical line and extended radio luminosities, with HEG being brighter than LEG in the [O III] line by a factor of ∼10. HEG and LEG are offset also in a plane that compares the black hole mass and the ionizing nuclear luminosity. However, although HEG are associated with higher nuclear luminosities, we find LEG among the brightest radio sources of the sample and with a clear FR II morphology, indistinguishable from those seen in HEG. This suggests that LEG are not simply objects with a lower level of accretion. We speculate that the differences between LEG and HEG are related to a different mode of accretion: LEG are powered by hot gas, while HEG require the presence of cold accreting material. The high temperature of the accreting gas in LEG accounts for the lack of "cold" structures (i.e. molecular torus and broad line region), for the reduced radiative output of the accretion disk, and for the lower gas excitation.

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Section: O Iii]/[o Ii] Line Ratiosupporting

confidence: 75%

An optical spectroscopic survey of the 3CR sample of radio galaxies withz$\mathsf{<}$ 0.3

Buttiglione¹,

Capetti

Celotti³

et al. 2010

A&A

257

390

View full text Add to dashboard Cite

show abstract

“…It is worth mentioning that the four 1FHL sources associated with radio galaxies have also shown characteristics that are typical for blazars, either in radio morphology (prominent flat-spectrum core with one-sided jet), in optical spectrum, or in γ -ray variability (sporadic short-term flux variability with timescales of 1 day). This is the case for PKS 0625−35 (e.g., see Wills et al 2004), M 87 (e.g., see Abramowski et al 2012), NGC 1275 (e.g., see Kataoka et al 2010;Aleksić et al 2012a), and IC 310 (e.g., see Kadler et al 2012;Shaw et al 2013;The MAGIC Collaboration et al 2013). The fifth radio galaxy, Cen A, is exceptional because of its proximity and also a presence of γ -ray emitting giant lobes clearly resolved with the LAT (Abdo et al 2010d).…”

Section: Description Of the 1fhl Catalogmentioning

confidence: 99%

THE FIRST FERMI -LAT CATALOG OF SOURCES ABOVE 10 GeV

Ackermann¹,

Ajello²,

Allafort³

et al. 2013

ApJS

221

180

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We present a catalog of γ -ray sources at energies above 10 GeV based on data from the Large Area Telescope (LAT) accumulated during the first 3 yr of the Fermi Gamma-ray Space Telescope mission. The first Fermi-LAT catalog of >10 GeV sources (1FHL) has 514 sources. For each source we present location, spectrum, a measure of variability, and associations with cataloged sources at other wavelengths. We found that 449 (87%) could be associated with known sources, of which 393 (76% of the 1FHL sources) are active galactic nuclei. Of the 27 sources associated with known pulsars, we find 20 (12) to have significant pulsations in the range >10 GeV (>25 GeV). In this work we also report that, at energies above 10 GeV, unresolved sources account for 27% ± 8% of the isotropic γ -ray background, while the unresolved Galactic population contributes only at the few percent level to the Galactic diffuse background. We also highlight the subset of the 1FHL sources that are best candidates for detection at energies above 50-100 GeV with current and future ground-based γ -ray observatories.

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“…This source has an optical classification of LERG, but is classified by Wills et al (2004) as a possible BL Lac object and by Gliozzi et al (2008) as a LERG. It has FRI morphology and lies in cluster A 3392 (Bgq ∼ 5000 -Ramos Almeida et al 2013).…”

Section: Pks 0404+03 (mentioning

confidence: 99%

The link between accretion mode and environment in radio-loud active galaxies

Ineson

Croston

Hardcastle

et al. 2015

Mon. Not. R. Astron. Soc.

130

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The interactions between radio-loud AGN and their environments play an important rôle in galaxy and cluster evolution. Recent work has demonstrated fundamental differences between High and Low Excitation Radio Galaxies (HERGs and LERGs), and shown that they may have different relationships with their environments. In the Chandra Large Project ERA (Environments of Radio-loud AGN), we made the first systematic X-ray environmental study of the cluster environments of radio galaxies at a single epoch (z ∼ 0.5), and found tentative evidence for a correlation between radio luminosity and cluster X-ray luminosity. We also found that this relationship appeared to be driven by the LERG sub-population (Ineson et al. 2013).We have now repeated the analysis with a low redshift sample (z ∼ 0.1), and found strong correlations between radio luminosity and environment richness and between radio luminosity and central density for the LERGs but not for the HERGs. These results are consistent with models in which the HERGs are fuelled from accretion discs maintained from local reservoirs of gas, while LERGs are fuelled more directly by gas ingested from the intra-cluster medium.Comparing the samples, we found that although the maximum environment richness of the HERG environments is similar in both samples, there are poorer HERG environments in the z ∼ 0.1 sample than in the z ∼ 0.5 sample. We have therefore tentative evidence of evolution of the HERG environments. We found no differences between the LERG subsamples for the two epochs, as would be expected if radio and cluster luminosity are related.

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Emission lines and optical continuum in low-luminosity radio galaxies

Cited by 77 publications

References 52 publications

An optical spectroscopic survey of the 3CR sample of radio galaxies withz$\mathsf{<}$ 0.3

An optical spectroscopic survey of the 3CR sample of radio galaxies withz$\mathsf{<}$ 0.3

THE FIRST FERMI -LAT CATALOG OF SOURCES ABOVE 10 GeV

The link between accretion mode and environment in radio-loud active galaxies

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