A New Hardware Correlator in Korea: Performance Evaluation Using KVN Observations

Lee, Sang-Sung; Oh, Chung Sik; Roh, Duk-Gyoo; Oh, Se-Jin; Kim, Jong-Soo; Yeom, Jae-Hwan; Kim, Hyo Ryoung; Jung, Dong-Gyu; Byun, Doyoung; Kawaguchi, Noriyuki; Shibata, Katsunori M.; Wajima, Kiyoaki

doi:10.5303/jkas.2015.48.2.125

Cited by 38 publications

(27 citation statements)

References 19 publications

(24 reference statements)

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“…The transferred digital signals were requantized and divided into 16 sub-bands (IFs) of 16 MHz wide by a digital filter bank, and recorded by the Mark 5B system at a recording rate of 1024Mbps. Correlation of the data was performed with the DiFX software correlator in the Korea-Japan Correlator Center (Lee et al 2015b). …”

Section: Observationsmentioning

confidence: 99%

INTERFEROMETRIC MONITORING OF GAMMA-RAY BRIGHT AGNs. I. THE RESULTS OF SINGLE-EPOCH MULTIFREQUENCY OBSERVATIONS

Lee

Wajima

Algaba

et al. 2016

ApJS

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We present results of single-epoch very long baseline interferometry (VLBI) observations of gamma-ray bright active galactic nuclei (AGNs) using the Korean VLBI Network (KVN) at the 22, 43, 86, and 129 GHz bands, which are part of a KVN key science program, Interferometric Monitoring of Gamma-Ray Bright AGNs. We selected a total of 34 radio-loud AGNs of which 30 sources are gamma-ray bright AGNs with flux densities of >6×10 −10 ph cm −2 s −1 . Single-epoch multifrequency VLBI observations of the target sources were conducted during a 24 hr session on 2013 November 19 and 20. All observed sources were detected and imaged at all frequency bands, with or without a frequency phase transfer technique, which enabled the imaging of 12 faint sources at 129 GHz, except for one source. Many of the target sources are resolved on milliarcsecond scales, yielding a core-jet structure, with the VLBI core dominating the synchrotron emission on a milliarcsecond scale. CLEAN flux densities of the target sources are 0.43-28 Jy, 0.32-21 Jy, 0.18-11 Jy, and 0.35-8.0 Jy in the 22, 43, 86, and 129 GHz bands, respectively. Spectra of the target sources become steeper at higher frequency, with spectral index means of −0.40, −0.62, and −1.00 in the 22-43 GHz, 43-86 GHz and 86-129 GHz bands, respectively, implying that the target sources become optically thin at higher frequencies (e.g., 86-129 GHz).

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Section: Observationsmentioning

confidence: 99%

INTERFEROMETRIC MONITORING OF GAMMA-RAY BRIGHT AGNs. I. THE RESULTS OF SINGLE-EPOCH MULTIFREQUENCY OBSERVATIONS

Lee

Wajima

Algaba

et al. 2016

ApJS

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“…The Mark5B system at a recording rate of 1024 Mbps was used for recording the data. The correlation was processed at the Korea-Japan Correlation Center (Yeom et al 2009;Lee et al 2015a). We corrected the visibility amplitude decrement due to the digital quantization loss and the characteristics of the KJCC, using the method of Lee et al (2015b).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Spatially Resolved HCN Absorption Features in the Circumnuclear Region of NGC 1052

Sawada-Satoh

Roh

et al. 2016

ApJL

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We present the first VLBI detection of HCN molecular absorption in the nearby active galactic nucleus NGC 1052. Utilizing the 1 mas resolution achieved by the Korean VLBI Network, we have spatially resolved the HCN absorption against a double-sided nuclear jet structure. Two velocity features of HCN absorption are detected significantly at the radial velocity of 1656 and 1719 km s −1 , redshifted by 149 and 212 km s −1 with respect to the systemic velocity of the galaxy. The column density of the HCN molecule is estimated to be 10 15 -10 16 cm −2 , assuming an excitation temperature of 100-230 K. The absorption features show high optical depth localized on the receding jet side, where the free-free absorption occurred due to the circumnuclear torus. The size of the foreground absorbing molecular gas is estimated to be on approximately one-parsec scales, which agrees well with the approximate size of the circumnuclear torus. HCN absorbing gas is likely to be several clumps smaller than 0.1 pc inside the circumnuclear torus. The redshifted velocities of the HCN absorption features imply that HCN absorbing gas traces ongoing infall motion inside the circumnuclear torus onto the central engine.

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“…Thanks to the unique capabilities of KVN, we obtained simultaneous dual polarization observations at two pairs of frequencies (either 22/43 GHz or 86/129 GHz). The observed data were correlated at the Korea-Japan Correlation Center (KJCC; Lee et al 2015).…”

Section: Observations and Data Reductionmentioning

confidence: 99%

Pagan I: Multi-Frequency Polarimetry of Agn Jets With KVN

Trippe

Sohn

et al. 2015

Journal of The Korean Astronomical Society

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Active Galactic Nuclei (AGN) with bright radio jets offer the opportunity to study the structure of and physical conditions in relativistic outflows. For such studies, multi-frequency polarimetric very long baseline interferometric (VLBI) observations are important as they directly probe particle densities, magnetic field geometries, and several other parameters. We present results from first-epoch data obtained by the Korean VLBI Network (KVN) within the frame of the P lasma Physics of Active Galactic N uclei (PAGaN) project. We observed seven radio-bright nearby AGN at frequencies of 22, 43, 86, and 129 GHz in dual polarization mode. Our observations constrain apparent brightness temperatures of jet components and radio cores in our sample to > 10 8.01 K and > 10 9.86 K, respectively. Degrees of linear polarization m L are relatively low overall: less than 10%. This indicates suppression of polarization by strong turbulence in the jets. We found an exceptionally high degree of polarization in a jet component of BL Lac at 43 GHz, with m L ∼ 40%. Assuming a transverse shock front propagating downstream along the jet, the shock front being almost parallel to the line of sight can explain the high degree of polarization.

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A New Hardware Correlator in Korea: Performance Evaluation Using KVN Observations

Cited by 38 publications

References 19 publications

INTERFEROMETRIC MONITORING OF GAMMA-RAY BRIGHT AGNs. I. THE RESULTS OF SINGLE-EPOCH MULTIFREQUENCY OBSERVATIONS

INTERFEROMETRIC MONITORING OF GAMMA-RAY BRIGHT AGNs. I. THE RESULTS OF SINGLE-EPOCH MULTIFREQUENCY OBSERVATIONS

Spatially Resolved HCN Absorption Features in the Circumnuclear Region of NGC 1052

Pagan I: Multi-Frequency Polarimetry of Agn Jets With KVN

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