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The Power of Simultaneous Multi-frequency Observations for mm-VLBI: Beyond Frequency Phase Transfer
Guang-Yao Zhao,Juan Carlos Algaba,Sang Sung Lee,Taehyun Jung,Richard Dodson,Maria Rioja,Do-Young Byun,Jeffrey Hodgson,Sincheol Kang,Dae-Won Kim,Jae-Young Kim,Jeong-Sook Kim,Soon-Wook Kim,Motoki Kino,A 한국천문학회 2017 天文學會報 Vol.42 No.1
Guang-Yao Zhao,Taehyun Jung,Bong Won Sohn,Motoki Kino,Mareki Honma,Richard Dodson,Maria Rioja,Seog-Tae Han,Katsunori Shibata,Do-Young Byun,Kazunori Akiyama,Juan-Carlos Algaba,Tao An,Xiaopeng Cheng,Ilj 한국천문학회 2019 Journal of The Korean Astronomical Society Vol.52 No.1
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 dualfrequency 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.
MULTI-EPOCH MULTI-FREQUENCY VLBI STUDY OF THE PARSEC-SCALE JET IN THE BLAZAR 3C 66A
Zhao, Guang-Yao,Chen, Yong-Jun,Shen, Zhi-Qiang,Sudou, Hiroshi,Iguchi, Satoru American Institute of Physics 2015 The Astronomical journal Vol.149 No.2
<P>We present observational results of the &ggr;-ray blazar 3C 66A at 2.3, 8.4, and 22 GHz at four epochs during 2004–2005 with the VLBA. The resulting images show an overall core-jet structure extending roughly to the south, with two intermediate breaks occurring in the region near the core. By model-fitting to the visibility data, the northmost component, which is also the brightest, is identified as the core according to its relatively flat spectrum and its compactness. Combining our results with previous results to investigate the proper motions of the jet components, we found the kinematics of 3C 66A to be quite complicated, with components of inward and outward, subluminal and superluminal motions all detected in the radio structure. The superluminal motions indicate strong Doppler boosting exists in the jet. The apparent inward motions of the innermost components last for at least 10 years and could not be caused by newborn components. A possible reason could be non-stationarity of the core due to opacity change.</P>
KVN SOURCE-FREQUENCY PHASE-REFERENCING OBSERVATION OF 3C 66A AND 3C 66B
ZHAO, GUANG-YAO,JUNG, TAEHYUN,DODSON, RICHARD,RIOJA, MARIA,SOHN, BONG WON The Korean Astronomical Society 2015 天文學論叢 Vol.30 No.2
In this proceedings, preliminary results of the KVN Source-Frequency Phase-Referencing (SFPR) observation of 3C 66A and 3C 66B are presented. The motivation of this work is to measure the core-shift of these 2 sources and study the temporal evolution of the jet opacity. Two more sources were observed as secondary reference calibrators and each source was observed at 22, 43, and 86 GHz simultaneously. Our preliminary results show that after using the observations at the lower frequency to calibrate those at the higher frequency of the same source, the residual visibility phases for each source at the higher frequencies became more aligned, and the coherence time became much longer; also, the residual phases for different sources, within 10 degrees angular separations, follow similar trends. After reference to the nearby calibrator, the SFPRed maps were obtained as well as the astrometric measurements, i.e. the combined coreshift. The measurements were found to be affected by structural blending effects because of the large beamsize of KVN, but this can be corrected with higher resolution maps (e.g. KAVA maps).
격물치지(格物致知)와 성현경계(聖賢境界) -률곡(栗谷)의 격물치지론(格物致知論)을 중심으로
팽요광 ( Yao Guang Peng ) (사)율곡연구원(구 사단법인 율곡학회) 2014 율곡학연구 Vol.28 No.-
格物致知를 工夫論의 핵심적 위치에 놓고 格物致知가 聖賢이 되는 데 얼마나 중요한 의미를 가지는지 아주 도드라지게 설명한 것이 栗谷 성리학의 중요한 특색이다. 이 글에서는 栗谷이 格物致知를 특별히 중시한 것이 ‘意는 情을 토대로 형성된다’라는 그의 심성론과 밀접한 관계가 있다고 보았다. 栗谷이 보기에 格物致知를 통해 意의 간섭을 克服하고 轉化시켜야만 진정으로 誠意、正心을 실현할 수 있다. 聖賢의 境界가 높고 낮음은 格物致知 工夫가 意를 轉化시킨 정도에 달려 있다는 말이다. Putting the theory concerning investigation of things and extension of knowledge in the core position of self-civilization (moral practice), which highlighted the importance of it to the realization of becoming a sage, constitutes the main characteristic of Yiyi`s neo-Confucianism. This essay holds the view that the reason why Yiyi paid so much attention to the theory of investigation of things and extension of knowledge owes to the close association between it and his theory of mind-nature featuring that intentions originate from emotion. As far as Yiyi is concerned, only by overcoming and transforming the distraction of intentions through investigation of things and extension of knowledge, can a person achieve sincerity and rectification of mind. Meanwhile, the difference in spiritual levels of the sages is also up to the degree of their transformation of intentions through investigation of things and extension of knowledge.
The Power of Simultaneous Multi-frequency Observations for mm-VLBI: Beyond Frequency Phase Transfer
Zhao, Guang-Yao,Algaba, Juan Carlos,Lee, Sang Sung,Jung, Taehyun,Dodson, Richard,Rioja, Marí,a,Byun, Do-Young,Hodgson, Jeffrey,Kang, Sincheol,Kim, Dae-Won,Kim, Jae-Young,Kim, Jeong-Sook,Kim, Soo American Institute of Physics 2018 The Astronomical journal Vol.155 No.1
<P>Atmospheric propagation effects at millimeter wavelengths can significantly alter the phases of radio signals and reduce the coherence time, putting tight constraints on high-frequency Very Long Baseline Interferometry (VLBI) observations. In previous works, it has been shown that non-dispersive (e.g., tropospheric) effects can be calibrated with the frequency phase transfer (FPT) technique. The coherence time can thus be significantly extended. Ionospheric effects, which can still be significant, remain however uncalibrated after FPT as well as the instrumental effects. In this work, we implement a further phase transfer between two FPT residuals (i.e., so-called FPT-square) to calibrate the ionospheric effects based on their frequency dependence. We show that after FPT-square, the coherence time at 3 mm can be further extended beyond 8 hr and the residual phase errors can be sufficiently canceled by applying the calibration of another source, which can have a large angular separation from the target (> 20 degrees) and significant temporal gaps. Calibrations for all-sky distributed sources with a few calibrators are also possible after FPT-square. One of the strengths and uniqueness of this calibration strategy is the suitability for high-frequency all-sky survey observations including very weak sources. We discuss the introduction of a pulse calibration system in the future to calibrate the remaining instrumental effects, allowing the possibility of imaging the source structure at high frequencies with FPT-square, where all phases are fully calibrated without involving any additional sources.</P>