안녕하십니까.

오늘 오후 4:00에 아래와 같이 2026년 상반기 정규 콜로키움이 진행될 예정입니다.

발표 후에는 연사와의 대화시간(5:00-5:40) 및 저녁 식사가 예정되어 있으니 많은 참여 부탁드립니다.

그리고 아래 온라인 회의 주소가 변경 되었으니 참고 바랍니다.

발표자: 김종서 박사 (Max Planck Institute for Radioastronomy)

호스트: Taehyun Jung 

장소: 장영실홀 331-2 및 원격 연결

일시: 3월 18일 (수) 오후 4:00

접속주소: https://us06web.zoom.us/j/84840334355?pwd=3FUkcuaYwNQwscjoUSo3ulk6KPPo6x.1

교육학점: 천문연 소속 현장참석자의 경우 필수 0.5 학점 부여

제목: Reconstructing Active Galactic Nuclei and Black Holes with Bayesian Radio Interferometric Imaging

초록: 

Radio interferometric imaging traditionally treats calibration and imaging as separate steps, using packages, such as AIPS, CASA, and DIFMAP. However, both processes rely on shared prior knowledge about the source and instrument. In this talk, I present a probabilistic calibration and imaging approach based on Bayesian imaging software resolve which jointly infers calibration and imaging parameters, naturally propagating calibration uncertainties into the final image reconstruction. Using variational inference to mitigate computational costs, this method achieves high-fidelity and super-resolved images while providing uncertainty estimates for calibration and imaging results. The framework is extended to include polarimetric calibration, enabling robust full-Stokes imaging.
I demonstrate the method using VLBI observations of active galactic nuclei (AGNs), including: M87 (VLBA and GMVA+ALMA, 43 and 86 GHz), revealing the black hole shadow and jet with improved resolution and quantified uncertainties in ring parameters, 3C273 (VLBA, 15 GHz), OJ287 (GMVA+ALMA, 86 GHz), and 3C120 (VLBA, 22 GHz) , producing reliable polarimetric images, instrumental calibration solutions (gains, D-terms), and rotation measure. Additional applications include the radio galaxy Hydra A (VLA, 2.5 GHz) and the microquasar SS433 (VLA, 5 GHz). I also present a Bayesian multi-frequency imaging method with frequency phase transfer (FPT) observations 4C39.25 (KaVA+Yebes, 22 and 44 GHz), enabling improved UV coverage and core shift measurements.
These results highlight the potential of Bayesian calibration and imaging to provide reliable reconstructions with quantified uncertainties, offering improved observational constraints on the innermost structures of black holes and their jet formation, and promising applications for next-generation radio interferometers.
 

진행언어: 영어

슬라이드언어: 영어

원격 접속 방법 :

A. 웹 브라우저: Chrome을 추천하며 아래 주소를 실행시 Zoom 구동을 위한 프로그램이 설치될 수 있음

B. 접속 주소: https://us06web.zoom.us/j/84840334355?pwd=3FUkcuaYwNQwscjoUSo3ulk6KPPo6x.1

C. 유의사항: 접속 후 "마이크는 뮤트로 설정" - 기본설정은 뮤트로 되어있음 > 질의 응답시간에는 마이크를 사용해서 질문 가능함

천문연 콜로키움 위원회 (김종수, 선광일, 이창원, 문홍규, 노혜림, 한정열)

운영위원회 (김진호, 홍준석, 석지연, 이재현, 유영삼, 송상헌)

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Dear all,

The KASI's regular colloquium is scheduled at Mar. 18, as shown below.

A conversation session with speakers and dinner are scheduled after the colloquium.

Please note that the Zoom link below has been updated due to an account issue.

Speaker: Dr. Jong-Seo Kim (Max Planck Institute for Radioastronomy)

Host: Taehyun Jung 

Place: Jang Yeong-sil Hall 331-2 & Online

Time: March 18 (Wed) 4:00 pm 

Access: https://us06web.zoom.us/j/84840334355?pwd=3FUkcuaYwNQwscjoUSo3ulk6KPPo6x.1

KASI Educational credits: 0.5 educational credits are awarded to off-line attendees.

Title: Reconstructing Active Galactic Nuclei and Black Holes with Bayesian Radio Interferometric Imaging

Abstract: 

Radio interferometric imaging traditionally treats calibration and imaging as separate steps, using packages, such as AIPS, CASA, and DIFMAP. However, both processes rely on shared prior knowledge about the source and instrument. In this talk, I present a probabilistic calibration and imaging approach based on Bayesian imaging software resolve which jointly infers calibration and imaging parameters, naturally propagating calibration uncertainties into the final image reconstruction. Using variational inference to mitigate computational costs, this method achieves high-fidelity and super-resolved images while providing uncertainty estimates for calibration and imaging results. The framework is extended to include polarimetric calibration, enabling robust full-Stokes imaging.
I demonstrate the method using VLBI observations of active galactic nuclei (AGNs), including: M87 (VLBA and GMVA+ALMA, 43 and 86 GHz), revealing the black hole shadow and jet with improved resolution and quantified uncertainties in ring parameters, 3C273 (VLBA, 15 GHz), OJ287 (GMVA+ALMA, 86 GHz), and 3C120 (VLBA, 22 GHz) , producing reliable polarimetric images, instrumental calibration solutions (gains, D-terms), and rotation measure. Additional applications include the radio galaxy Hydra A (VLA, 2.5 GHz) and the microquasar SS433 (VLA, 5 GHz). I also present a Bayesian multi-frequency imaging method with frequency phase transfer (FPT) observations 4C39.25 (KaVA+Yebes, 22 and 44 GHz), enabling improved UV coverage and core shift measurements.
These results highlight the potential of Bayesian calibration and imaging to provide reliable reconstructions with quantified uncertainties, offering improved observational constraints on the innermost structures of black holes and their jet formation, and promising applications for next-generation radio interferometers.
 

Language: English

Slide Language: English

Remote access procedure:

A. Web browser: Chrome - When executing the address below, a program for additional zoom operation can be installed.

B. Access: Go to  https://us06web.zoom.us/j/84840334355?pwd=3FUkcuaYwNQwscjoUSo3ulk6KPPo6x.1

C. Notice: After join, Please mute your microphone. - The default setting is microphone mute. > After the presentation, during the Q&A session, you can use the microphone to ask questions.

KASI Colloquium committee (Jongsoo Kim, Kwang-Il Seon, Chang Won Lee, Hong-Kyu Moon, Hyerim Noh, Jeong-Yeol Han)

Working committee (Jinho Kim, Junseok Hong,  Ji Yeon Seok, Jaehyun Lee, Young Sam Yu, Sanghun Song)