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On the connection of the apparent proper motion and the VLBI structure of compact radio sources

Created 17/10/2025

Updated 17/10/2025

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Many of the compact extragalactic radio sources that are used as fiducial points to define the celestial reference frame are known to have proper motions detectable with long-term geodetic/astrometric very long baseline interferometry (VLBI) measurements. These changes can be as high as several hundred microarcseconds per year for certain objects. When imaged with VLBI at milliarcsecond (mas) angular resolution, these sources (radio-loud active galactic nuclei) typically show structures dominated by a compact, often unresolved “core” and a one-sided “jet.” The positional instability of compact radio sources is believed to be connected with changes in their brightness distribution structure. For the first time, we test this assumption in a statistical sense on a large sample rather than on only individual objects. We investigate a sample of 62 radio sources for which reliable long-term time series of astrometric positions as well as detailed 8 GHz VLBI brightness distribution models are available. We compare the characteristic direction of their extended jet structure and the direction of their apparent proper motion. We present our data and analysis method, and conclude that there is indeed a correlation between the two characteristic directions. However, there are cases where the ∼1–10 mas scale VLBI jet directions are significantly misaligned with respect to the apparent proper motion direction. Citation: Moór, A., Frey, S., Lambert, S. B., Titov, O. A., & Bakos, J. (2011). On the connection of the apparent proper motion and the VLBI structure of compact radio sources. The Astronomical Journal, 141(6), 178. https://doi.org/10.1088/0004-6256/141/6/178

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Field Value
Title On the connection of the apparent proper motion and the VLBI structure of compact radio sources
Language eng
Licence Not Specified
Landing Page https://data.gov.au/data/dataset/729d385d-b445-405a-b047-444388f1d8b0
Contact Point
Geoscience Australia Data
clientservices@ga.gov.au
Reference Period
Geospatial Coverage
Map data © OpenStreetMap contributors
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Data Portal Geoscience Australia

Data Source

This dataset was originally found on Geoscience Australia "On the connection of the apparent proper motion and the VLBI structure of compact radio sources". Please visit the source to access the original metadata of the dataset:
https://ecat.ga.gov.au/geonetwork/srv/eng/csw/dataset/on-the-connection-of-the-apparent-proper-motion-and-the-vlbi-structure-of-compact-radio-sources