Speaker
Description
Active Galactic Nuclei (AGNs) are used by the space geodetic technique of very long baseline interferometry (VLBI) as references on the sky to precisely measure the shape and orientation of the Earth due to their extreme distances. Their positions form the celestial reference frame (CRF) that plays an important role in both astronomy and geodesy. The geodetic products and the CRF are determined by simultaneous VLBI observations at four frequency bands, centered at 3.3, 5.5, 6.6, and 10.5\,GHz. These quad-band observations are carried out by the new generation geodetic VLBI system, named VLBI Global Observing System. The AGNs in VGOS observations are all resolved at milli-arcsecond scales to have angular structure. Based on the different impacts, source structure can be divided into two parts: visible structure (large scales) and invisible structure (in beam sizes). The former one causes closure delays enlarging post-fit delay residuals in geodetic solutions whereas the latter causes source position changes. The study aims to model this time- and frequency-dependent source structure and to have the AGNs as point-like anchors on the sky for improving the accuracy of geodesy and astrometry. This study is funded by an ERC starting grant in 2023, the Astrogeodesy project, and it will also have a profound impact on the future VLBI facilities, such as SKA and ngVLA. I will report on the project and discuss the progress and challenges.
| What is your career stage? | Non-tenured scientist (post PhD) |
|---|---|
| Which telescopes do you use / are you affiliated with? | VGOS, VLA, SKA |
