The Introduction of a Priori Knowledge in Certain Processing Algorithms

Högbom, J. A.

doi:10.1007/978-94-009-9449-2_26

Cited by 12 publications

(7 citation statements)

References 1 publication

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“…Their visibility data were exported to be imaged with the difmap program package (Shepherd et al 1994). The hybrid mapping procedure was used with several cycles of cleaning (Högbom 1979) and phase self-calibration. Gain correction factors were determined in difmap and subsequently were used in aips to scale the amplitudes.…”

Section: Evn Datamentioning

confidence: 99%

The radio structure of the peculiar narrow-line Seyfert 1 galaxy candidate J1100+4421

Gabányi

Frey

Paragi

et al. 2017

Monthly Notices of the Royal Astronomical Society

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Narrow-line Seyfert 1 galaxies (NLS1) are an intriguing subclass of active galactic nuclei. Their observed properties indicate low central black hole mass and high accretion rate. The extremely radio-loud NLS1 sources often show relativistic beaming and are usually regarded as younger counterparts of blazars. Recently, the object SDSS J110006.07+442144.3 was reported as a candidate NLS1 source. The characteristics of its dramatic optical flare indicated its jet-related origin. The spectral energy distribution of the object was similar to that of the γ-ray detected radio-loud NLS1, PMN J0948+0022. Our high-resolution European Very Long Baseline Interferometry Network observations at 1.7 and 5 GHz revealed a compact core feature with a brightness temperature of 10 10 K. Using the lowest brightness temperature value and assuming a moderate Lorentz factor of ∼ 9 the jet viewing angle is 26 • . Archival Very Large Array data show a large-scale radio structure with a projected linear size of ∼ 150 kpc reminiscent of double-sided morphology.

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Section: Evn Datamentioning

confidence: 99%

The radio structure of the peculiar narrow-line Seyfert 1 galaxy candidate J1100+4421

Gabányi

Frey

Paragi

et al. 2017

Monthly Notices of the Royal Astronomical Society

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“…The calibrated data were then exported to the Difmap package (Shepherd et al 1994) for imaging. The conventional hybrid mapping procedure with subsequent iterations of CLEANing (Högbom 1979) and phase (then amplitude) self-calibration provided the images and brightness distribution models for the calibrators. Overall antenna gain correction factors were determined at the first step of the amplitude self-calibration.…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Four Dual Agn Candidates Observed With the Vlba

Gabányi¹,

Frey³

et al. 2016

ApJ

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According to hierarchical structure formation models, merging galaxies are expected to be seen in different stages of coalescence. However, there are currently no straightforward observational methods to either select or to confirm a large number of dual active galactic nucleus (AGN) candidates. Most attempts involve obtaining a better understanding of double-peaked narrow emission line sources, in order to distinguish the objects for which the emission lines originate from narrow-line kinematics or jet-driven outflows, from those which might harbor dual AGNs. We observed four such candidate sources with the Very Long Baseline Array (VLBA), at 1.5 GHz with a ∼10 mas angular resolution, for which the spectral profiles of AGN optical emission suggested the existence of dual AGNs. In SDSS J210449.13-000919.1 and SDSS J23044.82-093345.3 the radio structures are aligned with the optical emission features, thus the double-peaked emission lines might be the results of jet-driven outflows. In the third detected source SDSS J115523.74+150756.9, the radio structure is less extended and is oriented nearly perpendicular to the position angle derived from optical spectroscopy. The fourth source remained undetected with the VLBA, but it was imaged with the Very Large Array at arcsec resolution a few months before our observations, suggesting the existence of an extended radio structure. We did not detect two radio-emitting cores in any of the four sources, a convincing signature of duality.

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“…It is a typical double radio source with a regular FRII structure (Fanaroff & Riley 1974). It has been previously studied in with the WRST at 608 MHz, 1.4 and 5 GHz (Hogbom 1979;van Breugel & Jägers 1982;Jägers 1987) and at high resolution with the VLA at 1.4 GHz . The general characteristics of this source are presented in Table 2.…”

Section: C223mentioning

confidence: 99%

Low-frequency study of two giant radio galaxies: 3C 35 and 3C 223

Orrù

Murgia

Feretti

et al. 2010

A&A

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Aims. Radio galaxies with a projected linear size > ∼ 1 Mpc are classified as giant radio sources. According to the current interpretation these are old sources which have evolved in a low-density ambient medium. Because radiative losses are negligible at low frequency, extending spectral aging studies in this frequency range will allow us to determine the zero-age electron spectrum injected and then to improve the estimate of the synchrotron age of the source. Methods. We present Very Large Array images at 74 MHz and 327 MHz of two giant radio sources: 3C 35 and 3C 223. We performed a spectral study using 74, 327, 608 and 1400 GHz images. The spectral shape is estimated in different positions along the source. Results. The radio spectrum follows a power-law in the hotspots, while in the inner region of the lobe the shape of the spectrum shows a curvature at high frequencies. This steepening agrees with synchrotron aging of the emitting relativistic electrons. In order to estimate the synchrotron age of the sources, the spectra were fitted with a synchrotron model of emission. They show that 3C 35 is an old source of 143 ± 20 Myr, while 3C 223 is a younger source of 72 ± 4 Myr.

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The Introduction of a Priori Knowledge in Certain Processing Algorithms

Cited by 12 publications

References 1 publication

The radio structure of the peculiar narrow-line Seyfert 1 galaxy candidate J1100+4421

The radio structure of the peculiar narrow-line Seyfert 1 galaxy candidate J1100+4421

Four Dual Agn Candidates Observed With the Vlba

Low-frequency study of two giant radio galaxies: 3C 35 and 3C 223

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