DiFX-2: A More Flexible, Efficient, Robust, and Powerful Software Correlator

Deller, Adam T.; Brisken, Walter; Phillips, Chris; Morgan, John S.; Alef, W.; Cappallo, R. J.; Middelberg, E.; Romney, J. D.; Rottmann, Helge; Tingay, S. J.; Wayth, R. B.

doi:10.1086/658907

Cited by 417 publications

(359 citation statements)

References 14 publications

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“…Table 1). The data were correlated on the DiFX software correlator (Deller et al 2007(Deller et al , 2011 at Curtin University in Perth, Western Australia. The data were then calibrated and imaged following Ojha et al (2010).…”

Section: Atca Observationsmentioning

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: Atca Observationsmentioning

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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“…Correlation of RadioAstron experiments is performed at three different correlator facilities: the ASC RadioAstron correlator (Kardashev et al 2013;Andrianov et al 2014), the JIVE SFXC correlator (Kettenis 2010), and the DiFX software correlator (Deller et al 2007(Deller et al , 2011. In order to enable the correlation of RadioAstron data to be made in the DiFX correlator, the DiFX code has been upgraded by the Max-Planck-Institute for Radio Astronomy (MPIfR) in Bonn, addressing the specific aspects of data and telemetry formats of the SRT telescope on-board the Spektr-R spacecraft (Bruni 2014;Bruni et al 2015).…”

Section: Correlation Of Radioastron Experimentsmentioning

confidence: 99%

RadioAstron space VLBI imaging of polarized radio emission in the high-redshift quasar 0642+449 at 1.6 GHz

Lobanov

Gómez

Bruni

et al. 2015

A&A

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Context. Polarization of radio emission in extragalactic jets at a sub-milliarcsecond angular resolution holds important clues for understanding the structure of the magnetic field in the inner regions of the jets and in close vicinity of the supermassive black holes in the centers of active galaxies. Aims. Space VLBI observations provide a unique tool for polarimetric imaging at a sub-milliarcsecond angular resolution and studying the properties of magnetic field in active galactic nuclei on scales of less than 10 4 gravitational radii. Methods. A space VLBI observation of high-redshift quasar TXS 0642+449 (OH 471), made at a wavelength of 18 cm (frequency of 1.6 GHz) as part of the early science programme (ESP) of the RadioAstron mission, is used here to test the polarimetric performance of the orbiting Space Radio Telescope (SRT) employed by the mission, to establish a methodology for making full Stokes polarimetry with space VLBI at 1.6 GHz, and to study the polarized emission in the target object on sub-milliarcsecond scales. Results. Polarization leakage of the SRT at 18 cm is found to be within 9% in amplitude, demonstrating the feasibility of high fidelity polarization imaging with RadioAstron at this wavelength. A polarimetric image of 0642+449 with a resolution of 0.8 mas (signifying an ∼4 times improvement over ground VLBI observations at the same wavelength) is obtained. The image shows a compact corejet structure with low (≈2%) polarization and predominantly transverse magnetic field in the nuclear region. The VLBI data also uncover a complex structure of the nuclear region, with two prominent features possibly corresponding to the jet base and a strong recollimation shock. The maximum brightness temperature at the jet base can be as high as 4 × 10 13 K.

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“…Scans on 3C 345 were interleaved with observations of J1310+3233 (amplitude check, EVPA calibrator), J1407+2827 (D-term calibrator), and 3C 279 (amplitude check, EVPA calibrator). The VLBA data were correlated at the NRAO VLBA hardware correlator (Benson 1995) and starting from December 2009 the new VLBA-DiFX correlator was employed (Deller et al 2011). Analysis was done with NRAO's Astronomical Image Processing System (AIPS) and Caltech's Difmap (Shepherd et al 1995) software for imaging and modeling.…”

Section: Very Long Baseline Array (Vlba)mentioning

confidence: 99%

Relativistic outflow drivesγ-ray emission in 3C 345

Schinzel

Lobanov

Taylor

et al. 2012

A&A

100

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Aims. On the basis of the first 20 months of Fermi-LAT data and optical monitoring, the quasar 3C 345 has been identified as a γ-ray emitter. We investigate whether there is a connection between the γ-ray and optical variability of 3C 345 and the properties of its parsec-scale radio emission. Methods. We combined the Fermi-LAT data of 3C 345, covering an energy range of 0.1-300 GeV, with 32 Very Long Baseline Array observations of the object made at 43.2 GHz in the period of January 2008-March 2010.Results. The VLBA data reveal the morphology and kinematics of the flow on scales of up to ≈5 milliarcseconds (deprojected linear distances of 380 parsecs). The brightness temperature, T b (r), measured along the jet first decreases with distance ∝r −(0.95 ± 0.69) and later exhibits a break at ≈0.3 milliarcseconds (mas), with T b (r) ∝ r −(4.11 ± 0.85) at larger separations. Variations in the γ-ray, optical, and parsec-scale radio emission display a similar long-term trend that persists during the entire VLBA monitoring period. The γ-ray and optical variations on shorter timescales are related to structural changes in the jet on scales of ≈0.3 mas (≈23 parsecs, deprojected), with the γ-ray and optical flares possibly being related to the evolution of four distinct superluminal components identified in the flow. Conclusions. The observations indicate that both the quiescent and flaring components of the γ-ray emission are produced in a region of the jet that extends up to ∼23 pc. This region may correspond to the Compton-loss dominated zone of the flow and its large extent may favor the synchrotron self-Compton mechanism for γ-ray production in the relativistic jet of the quasar 3C 345.

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DiFX-2: A More Flexible, Efficient, Robust, and Powerful Software Correlator

Cited by 417 publications

References 14 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

RadioAstron space VLBI imaging of polarized radio emission in the high-redshift quasar 0642+449 at 1.6 GHz

Relativistic outflow drivesγ-ray emission in 3C 345

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