The Parsec-Scale Structure and Evolution of the Nearby Fanaroff-Riley Type II Radio Galaxy Pictor A

Tingay, S. J.; Jauncey, D. L.; Reynolds, John E.; Tzioumis, A. K.; McCulloch, P. M.; Ellingsen, S. P.; Costa, M. E.; Lovell, J. E. J.; Preston, R. A.; Simkin, S. M.

doi:10.1086/301283

Cited by 30 publications

(37 citation statements)

References 28 publications

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“…The corresponding upper limits to the jet viewing angles are thus θ j 20 • . Interestingly, mildly relativistic velocities are inferred for 3C 390.3 and Pictor A (β app up to 2.2 and 1.6, respectively; Kellermann et al 2004;Tingay et al 2000), both of which are good candidates for future Fermi-LAT detections (see Table 2 and Figure 8). These four BLRGs, not coincidentally, have the brightest radio/VLBI cores in the analyzed sample, consistent also with a relatively large degree of relativistic beaming (see the comment in the Appendix).…”

Section: Discussionmentioning

confidence: 94%

BROAD-LINE RADIO GALAXIES OBSERVED WITHFERMI-LAT: THE ORIGIN OF THE GeV γ-RAY EMISSION

Kataoka

Stawarz

Takahashi

et al. 2011

ApJ

100

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We report on a detailed investigation of the γ -ray emission from 18 broad-line radio galaxies (BLRGs) based on two years of Fermi Large Area Telescope data. We confirm the previously reported detections of 3C 120 and 3C 111 in the GeV photon energy range; a detailed look at the temporal characteristics of the observed γ -ray emission reveals in addition possible flux variability in both sources. No statistically significant γ -ray detection of the other BLRGs was found, however, in the considered data set. Though the sample size studied is small, what appears to differentiate 3C 111 and 3C 120 from the BLRGs not yet detected in γ -rays is the particularly strong nuclear radio flux. This finding, together with the indications of the γ -ray flux variability and a number of other arguments presented, indicates that the GeV emission of BLRGs is most likely dominated by the beamed radiation of relativistic jets observed at intermediate viewing angles. In this paper we also analyzed a comparison sample of high-accretion-rate Seyfert 1 galaxies, which can be considered radio-quiet counterparts of BLRGs, and found that none were detected in γ -rays. A simple phenomenological hybrid model applied for the broadband emission of the discussed radio-loud and radio-quiet type 1 active galaxies suggests that the relative contribution of the nuclear jets to the accreting matter is 1% on average for BLRGs, whereas it is 0.1% for Seyfert 1 galaxies.

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Section: Discussionmentioning

confidence: 94%

BROAD-LINE RADIO GALAXIES OBSERVED WITHFERMI-LAT: THE ORIGIN OF THE GeV γ-RAY EMISSION

Kataoka

Stawarz

Takahashi

et al. 2011

ApJ

100

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“…X-ray emission from the nucleus, the jet to the west of the nucleus, the western radio hot spot, and the eastern radio lobe was detected with Chandra (Wilson et al, 2001). Tingay et al (2000) found subluminal motions in the western jet. No parsec-scale counterjet has been detected so far.…”

Section: −458mentioning

confidence: 97%

TANAMI: tracking active galactic nuclei with austral milliarcsecond interferometry

Ojha¹,

Kadler

Böck³

et al. 2010

A&A

Self Cite

117

145

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Context. A number of theoretical models vie to explain the γ-ray emission from active galactic nuclei (AGN). This was a key discovery of EGRET. With its broader energy coverage, higher resolution, wider field of view and greater sensitivity, the Large Area Telescope (LAT) of the Fermi Gamma-ray Space Telescope is dramatically increasing our knowledge of AGN γ-ray emission. However, discriminating between competing theoretical models requires quasi-simultaneous observations across the electromagnetic spectrum. By resolving the powerful parsecscale relativistic outflows in extragalactic jets and thereby allowing us to measure critical physical properties, Very Long Baseline Interferometry observations are crucial to understanding the physics of extragalactic γ-ray objects. Results. We present first epoch images for 43 sources, some observed for the first time at milliarcsecond resolution. Parameters of these images as well as physical parameters derived from them are also presented and discussed. These and subsequent images from the TANAMI survey are available at http://pulsar.sternwarte.uni-erlangen.de/tanami/. Conclusions. We obtain reliable, high dynamic range images of the southern hemisphere AGN. All the quasars and BL Lac objects in the sample have a single-sided radio morphology. Galaxies are either double-sided, single-sided or irregular. About 28% of the TANAMI sample has been detected by LAT during its first three months of operations. Initial analysis suggests that when galaxies are excluded, sources detected by LAT have larger opening angles than those not detected by LAT. Brightness temperatures of LAT detections and non-detections seem to have similar distributions. The redshift distributions of the TANAMI sample and sub-samples are similar to those seen for the bright γ-ray AGN seen by LAT and EGRET but none of the sources with a redshift above 1.8 have been detected by LAT.

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“…Interpreting the variable component as unboosted (D ∼ 1) emission from a central blazar, and assuming standard jet parameters, the emission region would have an inclination angle to the line of sight of θ ≈ 25 • , and the observed factor-of-two increase in flux density within three years could be explained by a change of inclination angle by ≈3 • towards the observer. However, this would require a rotational speed significantly larger than that inferred from VLBI observations of the central jet of Pic A, if these are interpreted in a precessing jet model (Tingay et al 2000). An interpretation of the flare in Pic A as due to a shock in the jet would be more consistent with the misaligned-blazar picture: with a Doppler factor D ∼ 10 the Pic A flare would be comparable in intrinsic time scale and peak frequency with the exceptional outburst in 3C 454.3 observed in 2005.…”

Section: Variability In Unbeamed Sourcesmentioning

confidence: 99%

Long-term variability of extragalactic radio sources in thePlanckEarly Release Compact Source Catalogue

Chen

Rachen

López‐Caniego

et al. 2013

A&A

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Combining measurements taken using the Wilkinson Microwave Anisotropy Probe (WMAP) from 2001 to 2008 with measurements taken using Planck from 2009 to 2010, we investigate the long-term flux density variability of extragalactic radio sources selected from the Planck Early Release Compact Source Catalogue. The single-year, single-frequency WMAP maps are used to estimate yearly-averaged flux densities of the sources in the four WMAP bands: Ka (33 GHz), Q (41 GHz), V (61 GHz), and W (94 GHz). We identify 82, 67, 32, and 15 sources respectively as variable at greater than 99% confidence level in these four bands. The amplitudes of variation are comparable between bands, and are not correlated with either the flux densities or the spectral indices of the sources. The number counts of WMAP Ka-band sources are stable from year to year despite the fluctuation caused by individual source variability. Most of our sources show strong correlation in variability between bands. Almost all the sources that show variability are blazars. We have attempted to fit two simple, four-parameter models to the time-series of 32 sources showing correlated variability at multiple frequencies -a long-term flaring model and a rotating-jet model. We find that 19 sources (60%) can be fit with the simple rotating-jet model, and ten of these also fit the simple long-term flaring model. The remaining 13 sources (40%) show more complex variability behaviour that is not consistent with either model. Extended radio galaxies in our sample show no sign of variability, as expected, with the exception of Pictor A for which we report evidence for a millimetre flare lasting between 2002 and 2010.

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The Parsec-Scale Structure and Evolution of the Nearby Fanaroff-Riley Type II Radio Galaxy Pictor A

Cited by 30 publications

References 28 publications

BROAD-LINE RADIO GALAXIES OBSERVED WITHFERMI-LAT: THE ORIGIN OF THE GeV γ-RAY EMISSION

BROAD-LINE RADIO GALAXIES OBSERVED WITHFERMI-LAT: THE ORIGIN OF THE GeV γ-RAY EMISSION

TANAMI: tracking active galactic nuclei with austral milliarcsecond interferometry

Long-term variability of extragalactic radio sources in thePlanckEarly Release Compact Source Catalogue

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