Related papers: VLBI-Gaia offsets favor parsec-scale jet direction…
Significant positional offsets of the value from 1 mas to more than 10 mas were found previously between radio (VLBI) and optical (Gaia) positions of active galactic nuclei (AGN). They happen preferentially parallel to the parsec-scale jet…
Astrometry with the very long baseline radio interferometry (VLBI) allows to determine the position of a point close to the source's brightest compact detail at milliarcsecond scales. For most active galactic nuclei (AGNs), this compact…
We analyze differences in positions of active galactic nuclei between Gaia data release 2 and VLBI and compare the significant VLBI-to-Gaia offsets in more than 1000 objects with their jet directions. Remarkably at least 3/4 of the…
We interpret the recent discovery of a preferable VLBI/Gaia offset direction for radio-loud active galactic nuclei (AGNs) along the parsec-scale radio jets as a manifestation of their optical structure on scales of 1 to 100 milliarcseconds.…
Numerous studies have reported significant displacements in the coordinates of active galactic nuclei between measurements using radio interferometry techniques and those obtained by the Gaia space observatory. There is a consensus that…
Very long baseline interferometry (VLBI) observations show that some active galactic nuclei (AGN) jets exhibit bending even at parsec scales. The nature of bending is comprehensively analysed only for a small number of individual AGN, and…
When comparing modern fundamental reference frames in the radio (International Celestial Reference Frame) and optical (Gaia), a couple of bright radio reference sources appear to have very large radio-optical offsets, from tens up to…
In extragalactic jets, the apparent position of the bright/narrow end (the core) depends on the observing frequency, owing to synchrotron self-absorption and external absorption. The effect must be taken into account in order to achieve…
Active Galactic Nuclei (AGNs) observed with the technique of very long baseline interferometry (VLBI) are used as fiducial references on the sky to precisely measure the shape and orientation of the Earth. Their positions form a celestial…
We have cross matched the Gaia Data Release 1 secondary dataset that contains positions of 1.14 billion objects against the most complete to date catalogue of VLBI positions of 11.4 thousand sources, almost exclusively active galactic…
Context. It will soon become possible to directly link the most accurate radio reference frame with the Gaia optical reference frame using many common extragalactic objects. It is important to know the level of coincidence between the radio…
Dual and off-nucleus active supermassive black holes are expected to be common in the hierarchical structure formation paradigm, but their identification at parsec scales remains a challenge due to strict angular resolution requirements. We…
We present results from the highest resolution polarization imaging survey of a complete sample of extragalactic radio sources carried out to date. Our sample consists of a statistically complete flat-spectrum subset of 32 AGNs from the…
The direction of parsec-scale jets in active galactic nuclei (AGNs) is essential information for many astrophysical and astrometric studies, including linear polarization and magnetic field structure, frequency-dependent synchrotron…
We have analyzed the differences in positions of 9081 matched sources between the Gaia DR2 and VLBI catalogues. The median position uncertainty of matched sources in the VLBI catalogue is a factor of two larger than the median position…
The apparent position of the "core" in a parsec-scale radio jet (a compact, bright emitting region at the narrow end of the jet) depends on the observing frequency, owing to synchrotron self-absorption and external absorption. While…
Physical parameters of AGN jets observed with Very Long Baseline Interferometry (VLBI) are usually inferred from the core shift measurements or flux and size measured at a peak frequency of the synchrotron spectrum. Both are preceded by…
We study the relation between the VLBA (Very Long Baseline Array) radio emission at 15 GHz and the optical nuclear emission at 5100 A for a sample of 233 core-dominated AGN with relativistic jets. For 181 quasars, there is a significant…
The latest results of the most detailed analysis of multi-epoch polarization-sensitive observations of active galactic nuclei (AGN) jets at parsecs scales by very long baseline interferometry (VLBI) reveal several characteristic patterns of…
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…