Measuring the Core Shift Effect in Agn Jets With the Extended Korean Vlbi Network

Dodson, Richard; Han, Seog-Tae; Rioja, María J.; Byun, Doyoung; Honma, Mareki; Stevens, J.; Vicente, P. de; Sohn, Bong Won

doi:10.5303/jkas.2015.48.5.277

Cited by 10 publications

(11 citation statements)

References 21 publications

(26 reference statements)

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“…The time taken for the phase to rotate around 1 radian approaches several tens of minutes. Such an improvement in the coherence is comparable with those seen in the KVN-only experiments (e.g., Rioja et al 2014;Jung et al 2015) In order to quantify the extension of coherence time, we followed a simple procedure presented in Rioja et al (2012). We loaded the raw and FPTed data into Difmap and performed self-calibration over a series of integration times.…”

Section: Extension Of Coherence Timesmentioning

confidence: 69%

“…2008Zhao al. , 2013Jung et al 2015). The non-dispersive characteristics of tropospheric propagation effects (Rioja & Dodson 2011), which dominate the phase noise at high frequencies, lead to strong correlations between visibility phases at different frequencies (e.g., Jung et al 2011).…”

Section: Introductionmentioning

confidence: 99%

“…Non-KVN stations to have been upgraded with QO systems include the 4 VERA (VLBI Exploration of Radio Astrometry) stations in Japan and the Yebes 40m telescope in Spain. The Australia telescope compact array (ATCA) in Narrabri, Australia can also observe in dual-frequency mode with the KVN by sub-arraying its 6 antennas at different frequencies of 43/86 GHz as was successfully demonstrated in 2014 (e.g., Jung et al 2015). More stations with simultaneous observing capabilities such as the Mopra telescope in Australia will likely become available in the coming few years.…”

Section: Introductionmentioning

confidence: 99%

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Source-Frequency Phase-Referencing Observation of AGNs with KaVA Using Simultaneous Dual-Frequency Receiving

Zhao,

Jung,

Sohn

et al. 2019

Preprint

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The KVN(Korean VLBI Network)-style simultaneous multi-frequency receiving mode is demonstrated to be promising for mm-VLBI observations. Recently, other Very long baseline interferometry (VLBI) facilities all over the globe start to implement compatible optics systems. Simultaneous dual/multi-frequency VLBI observations at mm wavelengths with international baselines are thus possible. In this paper, we present the results from the first successful simultaneous 22/43 GHz dual-frequency observation with KaVA(KVN and VERA array), including images and astrometric results. Our analysis shows that the newly implemented simultaneous receiving system has brought a significant extension of the coherence time of the 43 GHz visibility phases along the international baselines. The astrometric results obtained with KaVA are consistent with those obtained with the independent analysis of the KVN data. Our results thus confirm the good performance of the simultaneous receiving systems for the non-KVN stations. Future simultaneous observations with more global stations bring even higher sensitivity and micro-arcsecond level astrometric measurements of the targets.

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Section: Extension Of Coherence Timesmentioning

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Source-Frequency Phase-Referencing Observation of AGNs with KaVA Using Simultaneous Dual-Frequency Receiving

Zhao,

Jung,

Sohn

et al. 2019

Preprint

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“…The baseline lengths between the KVN antennas range between 300 and 500 km, providing a spatial resolution ∼1 mas at the highest frequency band. Work is on-going to develop a global network of KVN-compatible antennas [71], which will provide tens of µ-as resolution.…”

Section: Astrometrymentioning

confidence: 99%

The science case for simultaneous mm-wavelength receivers in radio astronomy

Dodson¹,

Rioja²,

Gómez³

et al. 2017

New Astronomy Reviews

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This review arose from the European Radio Astronomy Technical Forum (ERATec) meeting held in Firenze, October 2015, and aims to highlight the breadth and depth of the high-impact science that will be aided and assisted by the use of simultaneous mm-wavelength receivers. Recent results and opportunities are presented and discussed from the fields of: continuum VLBI (observations of weak sources, astrometry, observations of AGN cores in spectral index and Faraday rotation), spectral line VLBI (observations of evolved stars and massive star-forming regions) and time domain observations of the flux variations arising in the compact jets of X-ray binaries. Our survey brings together a large range of important science applications, which will greatly benefit from simultaneous observing at mm-wavelengths. Such facilities are essential to allow these applications to become more efficient, more sensitive and more scientifically robust. In some cases without simultaneous receivers the science goals are simply unachievable. Similar benefits would exist in many other high frequency astronomical fields of research.

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“…With the unique simultaneous multi-frequency receiving system, the Korean VLBI network(KVN) would be the most suitable array to carry out millimeter astrometric observations (Jung et al 2015) phase-referencing (SFPR), which involves transferring phase calibrations first between frequencies and then among sources. In the same way relative positions between sources are measured by conventional phase-referencing, the combined core-shift of a pair of sources can be measured with SFPR (Rioja & Dodson 2011).…”

Section: Kvn Simultaneous Dual-frequency Observations Of Sgr A* (Cho mentioning

confidence: 99%

Millimeter VLBI observations of Sgr A* with KaVA and KVN

et al. 2016

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We present recent observation results of Sgr A* at millimeter obtained with VLBI arrays in Korea and Japan.7 mm monitoring of Sgr A* is part of our AGN large project. The results at 7 epochs during 2013-2014, including high resolution maps, flux density and two-dimensional size measurements are presented. The source shows no significant variation in flux and structure related to the G2 encounter in 2014. According to recent MHD simulations by kawashimaet al., flux and magnetic field energy can be expected to increase several years after the encounter; We will keep our monitoring in order to test this prediction.Astrometric observations of Sgr A* were performed in 2015 at 7 and 3.5 millimeter simultaneously. Source-frequency phase referencing was applied and a combined ”core-shift” of Sgr A* and a nearby calibrator was measured. Future observations and analysis are necessary to determine the core-shift in each source.

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Measuring the Core Shift Effect in Agn Jets With the Extended Korean Vlbi Network

Cited by 10 publications

References 21 publications

Source-Frequency Phase-Referencing Observation of AGNs with KaVA Using Simultaneous Dual-Frequency Receiving

Source-Frequency Phase-Referencing Observation of AGNs with KaVA Using Simultaneous Dual-Frequency Receiving

The science case for simultaneous mm-wavelength receivers in radio astronomy

Millimeter VLBI observations of Sgr A* with KaVA and KVN

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