<i>Spitzer</i>Reveals Hidden Quasar Nuclei in Some Powerful FR II Radio Galaxies

Ogle, Patrick; Whysong, D.; Antonucci, Robert

doi:10.1086/505337

Cited by 160 publications

(286 citation statements)

References 65 publications

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“…Table 3 lists the median values of important physical parameters for the four different classes. In general, our sample constitutes fairly lowluminosity sources with log νL total 408 MHz (median) = 41.6 erg s −1 compared to the sources detected by mid-infrared studies at intermediate redshift (Ogle et al 2006). …”

Section: Sample Selectionmentioning

confidence: 70%

“…We choose the division line between mid-infrared strong, hidden quasars and BLRGs, and weak, likely inactive, sources at νL core 11.85 μm = 2 × 10 43 erg s −1 , which is half the luminosity of the weakest BLRG in the midinfrared of our sample, Pictor A. This is four times lower than the dividing line that Ogle et al (2006) adopt using the same criterium. This difference is probably caused by our sample being at lower redshifts and our data, of higher resolution, shows more spread in core flux concentration.…”

Section: The Nature Of the Mid-infrared Emissionmentioning

confidence: 99%

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Dust tori in radio galaxies

Wolk¹,

Barthel²,

Peletier³

et al. 2010

A&A

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Aims. We investigate the quasar -radio galaxy unification scenario and detect dust tori within radio galaxies of various types. Methods. Using VISIR on the VLT, we acquired sub-arcsecond (∼0.40 ) resolution N-band images, at a wavelength of 11.85 μm, of the nuclei of a sample of 27 radio galaxies of four types in the redshift range z = 0.006−0.156. The sample consists of 8 edge-darkened, low-power Fanaroff-Riley class I (FR-I) radio galaxies, 6 edge-brightened, class II (FR-II) radio galaxies displaying low-excitation optical emission, 7 FR-IIs displaying high-excitation optical emission, and 6 FR-II broad emission line radio galaxies. Out of the sample of 27 objects, 10 nuclei are detected and several have constraining non-detections at sensitivities of 7 mJy, the limiting flux a point source has when detected with a signal-to-noise ratio of 10 in one hour of source integration. Results. On the basis of the core spectral energy distributions of this sample we find clear indications that many FR-I and several low-excitation FR-II radio galaxies do not contain warm dust tori. At least 57 ± 19 percent of the high-excitation FR-IIs and almost all of the broad line radio galaxies exhibit excess infrared emission, which must be attributed to warm dust reradiating accretion activity. The FR-I and low-excitation FR-II galaxies are all of low efficiency, which is calculated as the ratio of bolometric to Eddington luminosity L bol /L Edd < 10 −3 . This suggests that thick tori are absent at low accretion rates and/or low efficiencies. The high-excitation FR-II galaxies are a mixed population with three types of nuclei: 1) low efficiency with dust torus; 2) low efficiency with weakly emitting dust torus; and 3) high efficiency with weak dust torus. We argue that the unification viewing angle range 0-45 degrees of quasars should be increased to ∼60 degrees, at least at lower luminosities.

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Section: Sample Selectionmentioning

confidence: 70%

Section: The Nature Of the Mid-infrared Emissionmentioning

confidence: 99%

Dust tori in radio galaxies

Wolk¹,

Barthel²,

Peletier³

et al. 2010

A&A

View full text Add to dashboard Cite

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“…Rowan-Robinson 1995). Spitzer photometric and spectroscopic data have shown that the majority of high-z 3CR objects are luminous MIR emitters (Haas et al 2008;Leipski et al 2010), with observed MIR luminosities L 15 μm much higher than 8 × 10 43 ergs s −1 , the value separating hidden quasars from MIR weak radio galaxies at intermediate redshifts (Ogle et al 2006). There exists broad agreement that the AGN-heated nuclear dust is mainly located in clumps which are distributed in a toroidal pattern altogether referred to as the AGN torus (e.g.…”

Section: Fitting Componentsmentioning

confidence: 98%

Star formation inz> 1 3CR host galaxies as seen byHerschel

Podigachoski

Barthel

Haas

et al. 2015

A&A

122

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We present Herschel (PACS and SPIRE) far-infrared (FIR) photometry of a complete sample of z > 1 3CR sources, from the Herschel guaranteed time project The Herschel Legacy of distant radio-loud AGN. Combining these with existing Spitzer photometric data, we perform an infrared (IR) spectral energy distribution (SED) analysis of these landmark objects in extragalactic research to study the star formation in the hosts of some of the brightest active galactic nuclei (AGN) known at any epoch. Accounting for the contribution from an AGN-powered warm dust component to the IR SED, about 40% of our objects undergo episodes of prodigious, ULIRGstrength star formation, with rates of hundreds of solar masses per year, coeval with the growth of the central supermassive black hole. Median SEDs imply that the quasar and radio galaxy hosts have similar FIR properties, in agreement with the orientationbased unification for radio-loud AGN. The star-forming properties of the AGN hosts are similar to those of the general population of equally massive non-AGN galaxies at comparable redshifts, thus there is no strong evidence of universal quenching of star formation (negative feedback) within this sample. Massive galaxies at high redshift may be forming stars prodigiously, regardless of whether their supermassive black holes are accreting or not.

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“…However, observational evidence is mounting to suggest that this picture does not give a proper description for low-luminosity radioloud AGN (P 1.4 GHz < ∼ 10 25 W Hz −1 ). These objects produce weaker or no emission lines (Hine & Longair 1979;Jackson & Rawlings 1997), lack the dusty torus infrared emission (Ogle et al 2006), and do not produce the accretion related X-ray emission (Hardcastle et al 2006). It has been suggested that there are indeed two very different modes of AGN activity named the "Quasar mode" and the "Radio mode" (Best et al 2005;Hardcastle et al 2007).…”

Section: Introductionmentioning

confidence: 99%

The dependence of X-ray AGN activity on host galaxy properties and environment

Tasse

Röttgering

Best

2010

A&A

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There is mounting evidence that active galactic nuclei (AGN) selected through optical emission lines or radio luminosities comprise two distinct AGN populations, whose activity is triggered by different processes. In two previous papers, we studied the host galaxies and environment of radio-loud AGN. In this third paper we study the properties of a sample of Type-2 AGN that were selected on the basis of their [2-10] keV X-ray luminosity. We find that the X-ray luminosity function is in good agreement with previous studies and that the fraction of galaxies hosting an X-ray AGN is a strong function of the stellar mass of the host galaxy. The shape of this fraction-mass relation is similar to the fraction of galaxies that are emission-line AGN, while it differs significantly from the relation observed for radio-selected AGN. The AGN in our sample tend to be located in underdense environments where galaxy mergers and interactions are likely to occur. For all host galaxy masses, the Type-2 AGN display a strong infrared excess at short (∼3.5 μm) wavelengths, suggesting the presence of hot dust possibly associated with a hot dusty torus. These results add weight to the belief that the X-ray selection criteria identifies a population of AGN similar to the emission-line selected population but distinct from the radio population at high masses.

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SpitzerReveals Hidden Quasar Nuclei in Some Powerful FR II Radio Galaxies

Cited by 160 publications

References 65 publications

Dust tori in radio galaxies

Dust tori in radio galaxies

Star formation inz> 1 3CR host galaxies as seen byHerschel

The dependence of X-ray AGN activity on host galaxy properties and environment

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