Linear Polarization Imaging with Very Long Baseline Interferometry at High Frequencies

Leppänen, Kari; Zensus, J. A.; Diamond, P. J.

doi:10.1086/117706

Cited by 127 publications

(149 citation statements)

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“…Wardle et al have studied the polarization structure at 5 GHz of 3C 345 and interpreted their results in terms of a comprehensive shock model. First polarization images of 3C 345 at 22 GHz are basically in agreement with the interpretation by Wardle et al (Leppänen et al, 1995).…”

Section: · Curved Trajectories and Variable Speedssupporting

confidence: 90%

Parsec-Scale Structure of Compact Radio Sources

Zensus

1996

Symp. - Int. Astron. Union

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Abstract. High-dynamic range imaging and monitoring with Very Long Baseline Interferometry have considerably increased our knowledge of the parsec-scale properties of compact radio sources. I review some of the properties of individual sources in areas where particular progress has been made in the last few years. Imaging of Luminous ObjectsThe study of prominent flat-spectrum sources with Very Long Baseline Interferometry (VLBI) provides arguably the best opportunity for testing physical models of parsec-scale radio jets. Routine high-quality observations are possible with the Very Long Baseline Array (VLBA), the global VLBI campaigns with various other networks, and the "World Array" campaigns. At millimeter wavelengths, ad hoc arrays have been used to make images with highest resolution, albeit modest overall fidelity. Space VLBI missions in preparation bear the potential of imaging at yet higher resolution.For a review of the various VLBI surveys and for morphological classifications see Wilkinson (1995), and Vermeiden (these Proceedings) for a statistical analysis of superluminal motions. Here, I will focus on several recent results from various ongoing studies of individual objects. I will then review some of the results from detailed VLBI monitoring studies of specific sources.The high-luminosity VLBI sources typically have well collimated corejet structure at centimeter and millimeter wavelengths. The cores are identified based on compactness, flat radio spectra, and strong flux density variability. Stronger misalignment between the parsec-scale and the kiloparsec-

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Section: · Curved Trajectories and Variable Speedssupporting

confidence: 90%

Parsec-Scale Structure of Compact Radio Sources

Zensus

1996

Symp. - Int. Astron. Union

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“…The instrumental polarization (D-terms) was obtained using AIPS's task LPCAL (Leppanen et al 1995). Table 1 lists the instrumental polarization derived for each telescope, with Effelsberg as the reference antenna.…”

Section: Polarization Calibrationmentioning

confidence: 99%

PROBING THE INNERMOST REGIONS OF AGN JETS AND THEIR MAGNETIC FIELDS WITH RADIOASTRON. I. IMAGING BL LACERTAE AT 21 μas RESOLUTION

Gómez

Lobanov

Bruni

et al. 2016

ApJ

140

165

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We present the first polarimetric space very long baseline interferometry (VLBI) imaging observations at 22 GHz. BLLacertae was observed in 2013 November 10 with the RadioAstron space VLBI mission, including a ground array of 15 radio telescopes. The instrumental polarization of the space radio telescope is found to be less than 9%, demonstrating the polarimetric imaging capabilities of RadioAstron at 22 GHz. Ground-space fringes were obtained up to a projected baseline distance of 7.9Earth diameters in length, allowing us to image the jet in BLLacertae with a maximum angular resolution of 21 μas, the highest achieved to date. We find evidence for emission upstream of the radio core, which may correspond to a recollimation shock at about 40 μas from the jet apex, in a pattern that includes other recollimation shocks at approximately 100 and 250 μas from the jet apex. Polarized emission is detected in two components within the innermost 0.5 mas from the core, as well as in some knots 3 mas downstream. Faraday rotation analysis, obtained from combining RadioAstron 22 GHz and groundbased 15 and 43 GHz images, shows a gradient in rotation measure and Faraday-corrected polarization vector as a function of position angle with respect to the core, suggesting that the jet in BLLacertae is threaded by a helical magnetic field. The intrinsic de-boosted brightness temperature in the unresolved core exceeds 3 10 12 K, suggesting, at the very least, departure from equipartition of energy between the magnetic field and radiating particles.

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“…Polarization leakage parameters of the antennas (Dterms) were determined within AIPS with task LPCAL (Leppanen et al 1995). D-terms were examined for time stability (Roberts et al 1994;Gómez et al 2002) using the two polarizations of each IF at all antennas.…”

Section: Multi-epoch 4-43 Ghz Vlba Observationsmentioning

confidence: 99%

Multiwavelength observations of the γ-ray flaring quasar S4 1030+61 in 2009–2014

Kravchenko

Kovalev

Hovatta

2016

Mon. Not. R. Astron. Soc.

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We present a study of the parsec-scale multi-frequency properties of the quasar S4 1030+61 during a prolonged radio and γ-ray activity. Observations were performed within Fermi γ-ray telescope, OVRO 40-m telescope and MOJAVE VLBA monitoring programs, covering five years from 2009. The data are supplemented by four-epoch VLBA observations at 5, 8, 15, 24, and 43 GHz, which were triggered by the bright γ-ray flare, registered in the quasar in 2010. The S4 1030+61 jet exhibits an apparent superluminal velocity of (6.4±0.4)c and does not show ejections of new components in the observed period, while decomposition of the radio light curve reveals nine prominent flares. The measured variability parameters of the source show values typical for Fermi-detected quasars. Combined analysis of radio and γ-ray emission implies a spatial separation between emitting regions at these bands of about 12 pc and locates the γ-ray emission within a parsec from the central engine. We detected changes in the value and direction of the linear polarization and the Faraday rotation measure. The value of the intrinsic brightness temperature of the core is above the equipartition state, while its value as a function of distance from the core is well approximated by the power-law. Altogether these results show that the radio flaring activity of the quasar is accompanied by injection of relativistic particles and energy losses at the jet base, while S4 1030+61 has a stable, straight jet well described by standard conical jet theories.

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Linear Polarization Imaging with Very Long Baseline Interferometry at High Frequencies

Cited by 127 publications

References 0 publications

Parsec-Scale Structure of Compact Radio Sources

Parsec-Scale Structure of Compact Radio Sources

PROBING THE INNERMOST REGIONS OF AGN JETS AND THEIR MAGNETIC FIELDS WITH RADIOASTRON. I. IMAGING BL LACERTAE AT 21 μas RESOLUTION

Multiwavelength observations of the γ-ray flaring quasar S4 1030+61 in 2009–2014

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