The Southern Hemisphere VLBI experiment

Preston, R. A.; Jauncey, D. L.; Meier, D. L.; Tzioumis, A. K.; Ables, J. G.; Batchelor, R.; Faulkner, John; Gates, Joe; Greene, B.; Hamilton, P. A.; Harvey, Bruce; Haynes, R. F.; Johnson, Benjamin D.; Lambeck, Kurt; Louie, A. P.; McCulloch, P. M.; Moorey, G.; Morabito, D. D.; Nicolson, G. D.; Niell, A. E.; Robertson, James I.; Royle, G.; Skjerve, L. J.; Slade, M. A.; Slee, O. B.; Stolz, A.; Watkinson, Anne; Wehrle, A. E.; Wright, A. E.

doi:10.1086/115122

Cited by 47 publications

(26 citation statements)

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“…The covering factor f can thus be assumed to be the fraction of source flux density contained in the core and is best estimated from very long baseline interferometry (VLBI) observations of the radio source at the redshifted 21-cm line frequency; unfortunately, no such observations of PKS B0438−436 exist in the literature. The lowest frequency with published VLBI observations is 2.3 GHz, where most of the source flux density stems from two compact components, separated by 35 mas (Preston et al 1989). Of these, the north-west component is more compact than the south-east one (∼5 versus ∼18 mas) and is likely to be the nuclear core, especially as it is also very compact in higher resolution ( 2 mas) 4.8-GHz VLBI and VLBI Space Observatory Project (VSOP) images (Shen et al 1998;Tingay et al 2002).…”

Section: Discussionmentioning

confidence: 88%

“…Of these, the north-west component is more compact than the south-east one (∼5 versus ∼18 mas) and is likely to be the nuclear core, especially as it is also very compact in higher resolution ( 2 mas) 4.8-GHz VLBI and VLBI Space Observatory Project (VSOP) images (Shen et al 1998;Tingay et al 2002). The core has a flux density of ∼2.5 Jy in the 2.3-GHz VLBI image, ∼58 per cent of the total 2.3-GHz flux density (Preston et al 1989). Unfortunately, the source is highly variable and it is thus not possible to determine its spectral index or its core flux density at 424.3 MHz from the 2.3-and 4.8-GHz VLBI data, as these observations were carried out at very different epochs, many years before our observations.…”

Section: Discussionmentioning

confidence: 99%

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H i 21 cm absorption at z ∼ 2.347 towards PKS B0438-436

Kanekar

Subrahmanyan

Ellison

et al. 2006

Monthly Notices of the Royal Astronomical Society: Letters

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We report the detection of redshifted H i 21‐cm absorption in the z∼ 2.347 damped Lyman α absorber (DLA) towards PKS B0438−436 with the Green Bank Telescope. This is the second‐highest redshift at which 21‐cm absorption has been detected in a DLA. The absorption extends over ∼60 km s−1 and has two distinct components, at z= 2.347 477(12) and z= 2.347 869(20). A similar velocity structure is seen in optical metal lines, although the peak absorption here is offset by ∼11 km s−1 from the peak in the 21‐cm line. We obtain a high spin temperature Ts∼ (886 ± 248) × (f/0.58) K, using a covering factor estimated from 2.3‐GHz very long baseline interferometry data. However, the current data cannot rule out a low spin temperature. The non‐detection of CO 3–2 absorption places the upper limit NCO < 3.8 × 1015 (Tx/10) cm−2 on the CO column density.

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Section: Discussionmentioning

confidence: 88%

Section: Discussionmentioning

confidence: 99%

H i 21 cm absorption at z ∼ 2.347 towards PKS B0438-436

Kanekar

Subrahmanyan

Ellison

et al. 2006

Monthly Notices of the Royal Astronomical Society: Letters

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“…MRC B0208−512: VLBI modelling shows a strong core (Preston et al 1989), and a jet-like feature (Tingay et al 1996). Detected as an X-ray source in the ROSAT All-Sky Survey (Brinkmann et al 1994) and as a γ-ray source in the EGRET survey (Bertsch et al 1993).…”

Section: Individual Sourcesmentioning

confidence: 99%

“…A VLBI image shows a 90 mas double structure (King et al 1993). MRC B1215−457: Compact steep-spectrum source with a strong, slightly resolved VLBI core (Preston et al 1989). MRC B1234−504: Compact steep-spectrum source, with no optical counterpart on the UK Schmidt sky survey but possible stellar identification on a CCD image obtained at the Anglo-Australian Telescope (AAT) (Burgess 1998).…”

Section: Individual Sourcesmentioning

confidence: 99%

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Long-term Monitoring of Molonglo Calibrators

Gaensler

Hunstead

2000

Publ. – Astron. Soc. Aust

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Before and after every 12 hour synthesis observation, the Molonglo Observatory Synthesis Telescope (MOST) measures the flux densities of ∼5 compact extragalactic radio sources, chosen from a list of 55 calibrators. From 1984 to 1996, the MOST made some 58,000 such measurements. We have developed an algorithm to process this dataset to produce a light curve for each source spanning this thirteen-year period. We find that 18 of the 55 calibrators are variable, on time scales between one and ten years. There is the tendency for sources closer to the Galactic Plane to be more likely to vary, which suggests that the variability is a result of refractive scintillation in the Galactic interstellar medium. The sources with the flattest radio spectra show the highest levels of variability, an effect possibly resulting from differing orientations of the radio axes to the line of sight.

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TANAMI: Multiwavelength and multimessenger observations of active galaxies

2015

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Extragalactic jets launched from the immediate vicinity of supermassive black holes in radio-loud active galactic nuclei (AGN) are key objects in modern astronomy and astroparticle physics. AGN jets carry a fraction of the total gravitational energy released during the accretion of matter onto supermassive black holes and are prime suspects as possible sources of ultrahigh-energy cosmic rays and the recently detected extraterrestrial neutrinos at PeV energies. TANAMI (Tracking Active galactic Nuclei with Austral Milliarcsecond Interferometry) is a multiwavelength program monitoring AGN jets of the southern sky. It combines high-resolution imaging and spectral monitoring at radio wavelengths with higher-frequency observations at IR, optical/UV, X-ray, and γ-ray energies. We review recent results of the TANAMI program, highlighting AGN candidate neutrino-emitters in the error circles of the IceCube PeV neutrino events.

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The Southern Hemisphere VLBI experiment

Cited by 47 publications

References 0 publications

H i 21 cm absorption at z ∼ 2.347 towards PKS B0438-436

H i 21 cm absorption at z ∼ 2.347 towards PKS B0438-436

Long-term Monitoring of Molonglo Calibrators

TANAMI: Multiwavelength and multimessenger observations of active galaxies

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