TANAMI: Multiwavelength and multimessenger observations of active galaxies

Kadler, M.; Ojha, R.; Collaboration, TANAMI

doi:10.1002/asna.201512186

Cited by 11 publications

(12 citation statements)

References 61 publications

(59 reference statements)

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“…This is the second in a series of papers presenting results from broadband observations of PKS 2004−447. The observations reported in this series were conducted as part of the TANAMI 2 multiwavelength programme (Ojha et al 2010;Kadler et al 2015) that monitors γ-ray loud AGNs south of −30 • declination. In a separate paper (Kreikenbohm et al 2016, hereafter Paper I), we discussed X-ray observations with XMM-Newton and Swift, finding a flat blazar-like power law and moderate variability on time scales down to months with an observed luminosity of (0.7-2.6) ×10 44 erg/s.…”

Section: Introductionmentioning

confidence: 99%

The gamma-ray emitting radio-loud narrow-line Seyfert 1 galaxy PKS 2004−447

Schulz

Kreikenbohm

Kadler

et al. 2016

A&A

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Context. Γ-ray-detected radio-loud narrow-line Seyfert 1 (γ-NLS1) galaxies constitute a small but interesting sample of the γ-ray-loud AGN. The radio-loudest γ-NLS1 known, PKS 2004−447, is located in the southern hemisphere and is monitored in the radio regime by the multiwavelength monitoring programme TANAMI. Aims. We aim for the first detailed study of the radio morphology and long-term radio spectral evolution of PKS 2004−447, which are essential for understanding the diversity of the radio properties of γ-NLS1s. Methods. The TANAMI VLBI monitoring program uses the Australian Long Baseline Array (LBA) and telescopes in Antarctica, Chile, New Zealand, and South Africa to monitor the jets of radio-loud active galaxies in the southern hemisphere. Lower resolution radio flux density measurements at multiple radio frequencies over four years of observations were obtained with the Australia Telescope Compact Array (ATCA). Results. The TANAMI VLBI image at 8.4 GHz shows an extended one-sided jet with a dominant compact VLBI core. Its brightness temperature is consistent with equipartition, but it is an order of magnitude below other γ-NLS1s with the sample value varying over two orders of magnitude. We find a compact morphology with a projected large-scale size <11 kpc and a persistent steep radio spectrum with moderate flux-density variability. Conclusions. PKS 2004−447 appears to be a unique member of the γ-NLS1 sample. It exhibits blazar-like features, such as a flat featureless X-ray spectrum and a core-dominated, one-sided parsec-scale jet with indications for relativistic beaming. However, the data also reveal properties atypical for blazars, such as a radio spectrum and large-scale size consistent with compact-steep-spectrum (CSS) objects, which are usually associated with young radio sources. These characteristics are unique among all γ-NLS1s and extremely rare among γ-ray-loud AGN.

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Section: Introductionmentioning

confidence: 99%

The gamma-ray emitting radio-loud narrow-line Seyfert 1 galaxy PKS 2004−447

Schulz

Kreikenbohm

Kadler

et al. 2016

A&A

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“…An extensive multiwavelength study of PMN J1603-4904 (Müller et al 2014(Müller et al , 2015, conducted within the framework of the TANAMI program (Ojha et al 2010;Kadler et al 2015), suggested it was not a blazar. Very Long Baseline Interferometry (VLBI) observations indicate a CSO-like morphology.…”

Section: Introductionmentioning

confidence: 99%

The MHz-peaked radio spectrum of the unusualγ-ray source PMN J1603–4904

Müller

Burd

Schulz

et al. 2016

A&A

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Context. The majority of bright extragalactic γ-ray sources are blazars. Only a few radio galaxies have been detected by Fermi/LAT. Recently, the GHz-peaked spectrum source PKS 1718-649 was confirmed to be γ-ray bright, providing further evidence for the existence of a population of γ-ray loud, compact radio galaxies. A spectral turnover in the radio spectrum in the MHz to GHz range is a characteristic feature of these objects, which are thought to be young due to their small linear sizes. The multiwavelength properties of the γ-ray source PMN J1603-4904 suggest that it is a member of this source class. Aims. The known radio spectrum of PMN J1603-4904 can be described by a power law above 1 GHz. Using observations from the Giant Metrewave Radio Telescope (GMRT) at 150, 325, and 610 MHz, we investigate the behavior of the spectrum at lower frequencies to search for a low-frequency turnover. Methods. Data from the TIFR GMRT Sky Survey (TGSS ADR) catalog and archival GMRT observations were used to construct the first MHz to GHz spectrum of PMN J1603-4904. Results. We detect a low-frequency turnover of the spectrum and measure the peak position at about 490 MHz (rest-frame), which, using the known relation of peak frequency and linear size, translates into a maximum linear source size of ∼1.4 kpc. Conclusions. The detection of the MHz peak indicates that PMN J1603-4904 is part of this population of radio galaxies with turnover frequencies in the MHz to GHz regime. Therefore it can be considered the second confirmed object of this kind detected in γ-rays. Establishing this γ-ray source class will help to investigate the γ-ray production sites and to test broadband emission models.

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“…Note the different angular resolutions and beam shapes for each epoch due to the different configurations of the TANAMI VLBI array. See also the corresponding proper motion movie presented in Kadler et al (2015). the jet flow is interrupted and widens up, but remains collimated downstream.…”

Section: The "Tuning Fork"mentioning

confidence: 94%

“…As an illustration of the plasma motion in the jet, we produced a movie using the individual VLBI images interpolated in time (Fig. 7), as reported in Kadler et al (2015). It can be accessed at http://www.aip.de/AN/movies.…”

Section: Sub-parsec Scale Jet Kinematicsmentioning

confidence: 99%

“…Since 2011, the (u, v)-coverage (see as an example Fig. 1) at intermediate baselines is significantly improved by the Warkworth (New Zealand), Katherine and Yarragadee (Australia) antennas (Kadler et al 2015). TANAMI observations typically have an angular resolution of about a few mas, down to less than 1 mas, with the largest baselines to the transoceanic antennas Hartebeeshoeck, TIGO and O'Higgins.…”

Section: Introductionmentioning

confidence: 99%

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Multiwavelength and parsec‐scale properties of extragalactic jets

Müller

2016

Astron Nachr

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Extragalactic jets originating from the central supermassive black holes of active galaxies are powerful, highly relativistic plasma outflows, emitting light from the radio up to the γ-ray regime. The details of their formation, composition and emission mechanisms are still not completely clear. The combination of high-resolution observations using very long baseline interferometry (VLBI) and multiwavelength monitoring provides the best insight into these objects. Here, such a combined study of sources of the TANAMI sample is presented, investigating the parsec-scale and high-energy properties. The TANAMI program is a multiwavelength monitoring program of a sample of the radio and γ-ray brightest extragalactic jets in the southern sky, below −30• declination. We obtain the first-ever VLBI images for most of the sources, providing crucial information on the jet kinematics and brightness distribution at milliarcsecond resolution. Two particular sources are discussed in detail: PMN J1603−4904, which can be classified either as an atypical blazar or a γ-ray loud (young) radio galaxy, and Centaurus A, the nearest radio-loud active galaxy. The VLBI kinematics of the innermost parsec of Centaurus A's jet result in a consistent picture of an accelerated jet flow with a spine-sheath like structure.

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TANAMI: Multiwavelength and multimessenger observations of active galaxies

Cited by 11 publications

References 61 publications

The gamma-ray emitting radio-loud narrow-line Seyfert 1 galaxy PKS 2004−447

The gamma-ray emitting radio-loud narrow-line Seyfert 1 galaxy PKS 2004−447

The MHz-peaked radio spectrum of the unusualγ-ray source PMN J1603–4904

Multiwavelength and parsec‐scale properties of extragalactic jets

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